Current Affairs 6th Class

                                                                 Living Organisms and their Habitats   Plants There are a large number of plants in our surroundings. Plants are living things which can make their own food. They are vital for the survival of animals including us. Let's study about the plants in some detail.   Classification of Plants on the Basis of Bearing Flowers All the plants has been divided into two groups on the basis that either they bear flowers or not.   Flowering Plants: The plants, which bear flowers, are called flowering plants. For example, rose, mango, sunflower, grass, lemon, tulsi, peepal, etc.   Non-Flowering Plants: The plants, which do not bear flowers, are called non-flowering plants. For example, ferns, mosses, algae, fungi, etc.   Classification of Plants on the Basis of Size, Nature of Stem and Life-span   Herbs Herbs are small plants which have a soft and delicate stem. They have short life-span. They live for only one or two season. For example, grass, tomato, wheat, paddy, cabbage, etc. Banana plant is a herb.   Shrubs Shrubs are medium sized plants which have hard but not very thick stem. Their life-span is for many years but less than that of trees. For example, rose, lemon, jasmine, etc.   Trees Trees are tall and big plants which have hard brown thick stem. Their life-span is for many years. For example, mango, neem, palm, coconut, etc.   Climbers Climber plants have long, thin and weak stem so they cannot stand upright. They climb up with the help of a support. For example, pea plants, grape vine, glory lily, jasmine, etc.   Creepers Creeper plants also have long, thin, and weak stem. Creeper plants do not have special organ for climbing up so they spread out on the ground. For example, strawberry, pumpkin, cucumber, etc.   Parts of a Plant Root, stem, leaves, flowers and fruits are the main parts of plants.   Root This part of a plant grows below the ground. Root fixes the plant firmly to the soil. It also absorbs water and minerals from the soil which are essential for the photosynthesis.   Types of Roots There are mainly two types of roots: tap root and fibrous root.   Tap root: It consists of a main root called tap root from which a number of branching roots arise called lateral roots. For example, mango, radish, mustard, etc.                            Fibrous root: It consists of many thin, fibre-like roots arising from the base of the stem. For example, grass, wheat, paddy, maize, etc.                                     Stem It grows vertically up from the ground.   Functions of Stem:
  • It holds the plants upright.
  • It bears more...

  Body Movements   Body Movements When we move our body parts like mouth, head, arms, hands and fingers, etc, then our body may remain at the same place. But when we walk by using legs, then we move our whole body from one place to another. The ability of a human being to move its body from one place to another, is called locomotion.   The Skeletal System The human skeleton or skeletal system is made up of 206 bones. A baby has 300 bones in all. But as it grows, some of the bones fuse together or join. Before we learn more about bones and the joints and where they are joined together, let us take a look at the functions of the skeletal system.   Functions The bones of our body act as a framework or give a shape to our body. Without bones, our body could be a shapeless mass, say like the body of a snail. It is the movement of the bones that helps us bend, run, walk and so on.   The Skull Twenty-two bones make up the skull. These are the hardest of all the bones in the body. Some of these form the cranium, or the cover for the brain. All the bones of the skull except the one forming the lower jaw are fixed firmly, and cannot move. Only the bone of the lower jaw is capable of movement, which helps us to eat and speak.     Most of the bones of the skull are fixed. Only the lower jaw can move.   The Spine The spine also called the vertebral column or backbone, the spine consists of 33 small bones known as vertebrae (singular: vertebra). The vertebrae are hollow at the centre and are joined together to form a tube, through which runs the spinal cord. One of the functions of the vertebral column is to protect the spinal cord. The other functions are to hold the body up and help us bend forward, backward, sideways and twist from the waist.   The Ribcage Running through the centre of the chest is the breastbone or sternum. Joined to it are 10 pairs of strong, flexible bones called ribs. The ribs curve around and join the chest vertebrae at the back, to form a protective cover for the lungs and heart, called the ribcage. Another two pairs of ribs are joined only to the backbone. These are called floating ribs. The ribs are attached to the sternum in such a way as to allow the ribcage to expand when we inhale, or breathe in and contract when we exhale, or breathe out.   The Shoulder Bones In shoulder bone each collar bone (clavicle) is attached to a shoulder blade (scapula) and to the breastbone.   Shoulder Bones   The Bones of more...

  Motion and Measurement of Distance   Physical Quantities The quantities like length, mass, time etc. that can be measured are called physical quantities.   Measurement: It is the comparison of an unknown quantity with a certain fixed quantity of the same kind.   Unit of Measurement: A unit of measurement is a definite magnitude of a physical quantity. For example metre, centimetre, kilometre etc are units of length.   Standard Unit: For the sake of uniformity, scientists all over the world have accepted a system of units called Sl System. In the SI the System
  • The unit of length is metre (m).
  • The unit of mass is kilogram (kg).
  • The unit of time is second (s).
  • Other system used are FPS, CGS and MKS.
  Multiples and Submultiples of Units Length 1 centimetre (cm) = 10 millimetres 1 decimetre (dm) = 10 centimetres = 100 mm 1 metre (m) = 100 centimetres 1 metre (m) = 1000 millimetres 1 kilometre (km) = 1000 metres   Mass 1 gram (g) = 1000 milligrams 1 kilogram (kg) = 1000 grams 1 kilogram (kg) = 1000000 milligrams 1 quintal = 100 kilograms 1 metric ton = 1000 kilograms   Time 1 minute = 60 seconds 1 hour = 60 minutes 1 day= 24 hours 1 year=365 days 1 century= 100 years 1 millennium = 1000 years   Motion If an object changes its position with respect to time, the body is said to be in motion. If an object does not change its position with respect to time, the object is said to be at rest.   Types of Motion There are different types of motions. Let us know about them.   Rectilinear Motion: Motion in a straight path. For example, car moving on straight road.   Circular Motion: Motion in a circular path. For example, toy train moving on a circular path.   Periodic Motion: The motion which repeats itself after a regular interval of time. For example, motion of hands of clock.       Rotational Motion: Spinning of an object about a fixed axis. For example, motion giant wheel and rotation of earth.        

  Light, Shadow and Reflection   Light Light is a form of energy visible to the human eye that is radiated by moving charged particles. Speed of light in air is about\[3\times {{10}^{8}}m\text{/}s\].   Ray: It is a very narrow and straight path of light.   Beam: It is broader and consists of several rays.   Sources of Light The objects which give out light are called sources of light. Sun, star, bulb, torch, candle, lantern, lamp, etc. are the sources of light.   Luminous and Non-luminous Objects The objects which produce their own light are called luminous objects. Sun, stars, bulb, torch, candle, lantern, lamp etc. are luminous objects. The objects which do not produce light on their own are called non-luminous objects. Table, fan, book, chair, etc. are non-luminous objects.   Transparent, Translucent and Opaque Objects Transparent Objects: The objects which allow light to pass through them. For example glass, water, air, etc.   Translucent Objects: The objects which allow light to pass through them partially. For example, oiled paper, tissue paper, muddy water, ground glass, etc.   Opaque Objects: The objects which do not allow light to pass through them. For example, wall, blackboard, metal sheet, etc.   Shadow If an object is placed in front of a source of light, the object cast its shade which is known as shadow. All the opaque objects produce their shadow on the opposite side to the source of light. The shape of shadow depends on the followings:
  • Shape of the object
  • Size of the source of light
  • Position of the source of light
  Reflection of Light When a ray of light falls on the surface of a mirror, they are sent back. This phenomenon is known as reflection of light.       (r=angle of reflection) = (i=angle of incidence) The ray which falls on the surface of a mirror is called an incident ray. The ray which is sent back after reflection is called reflected ray.   Spherical Mirrors A spherical mirror is a mirror which has the shape of a piece cut out of a spherical surface. There are two types of spherical mirrors: concave and convex.     Reflecting surface of a concave mirror bulges inward whereas reflecting surface of a convex mirror bulges outward.   Images Real Image The images which are inverted and can be taken on the screen are called real images   Virtual Image The images which are erect and cannot be taken on the screen are called virtual images.    

  Electricity and Magnets   Electricity Electricity is a form of energy called electrical energy. We can convert electrical energy into various other forms of energies easily.   Electric Circuit The path through which electric current can flow is known as electric circuit. A simple electric circuit is made up of a bulb, wire and an electric cell. An electric cell has two terminals: a positive terminal and a negative terminal. A wire is connected from positive terminal to negative terminal of the cell and the bulb is connected to the wire so that current can flow through bulb.       Closed Circuit: When there is no gap in an electric circuit or the normal path of current has not been interrupted, the circuit is known as closed or complete circuit.   Open Circuit: When there is a gap in an electric circuit or the normal path of current has been interrupted, the circuit is known as an open circuit or incomplete circuit.   Conductors and Insulators The substances which allow electric current to pass through them are called conductors. For example, copper, gold, silver, aluminium, iron, etc. are good conductors of electricity. The substances which do not allow electric current to pass through them are called insulators. For example, wood, plastic, paper, rubber, etc are insulators.   Electric Cell An electric cell is a device which can generate electric current in a closed circuit. It is small and easily portable so it is very useful for us. There are a number of machines like watches, calculators, toys, cars, etc. in which electrical cell is used to produce electric current. Dry cell, button cell, solar cell are the examples of electric cell.   Dry Cell A dry cell is a cylindrical device in which a number of chemicals are stored. It has a metal cap on one side called positive terminal and a metal sheet at other side called negative terminal. It produces electric current from the chemical stored inside it.         Electric Bulb An electric bulb is a device which produces light energy using electrical energy. It consists of a glass bulb fixed on a metal case, a thin wire fixed between the two thick wires called filament of the bulb and the gas filled inside the glass bulb. When electric current passes through the filament, it emits light which makes the bulb glow.     Magnet Magnet is a substance which attracts magnetic materials such as iron, nickel, steel and cobalt. Magnets are of different shapes and sizes. For example, U-shaped magnet, cylindrical magnet, bar magnet, etc. Each magnet has two poles, south pole and north pole.   Magnetic Materials: The materials which are attracted by a magnet are called magnetic materials. For example, iron, nickel, steel and cobalt are magnetic materials. Magnetic materials more...

  Environment   Water Water is an abiotic component of the environment which is essential for the survival of life on the earth. It is present on the earth in all three states solid, liquid and gas. It covers about 71% of the earth surface.   Importance of Water It is the water which makes life possible on earth. Without water existence of life was not possible on the earth. Therefore, water is very important for all of us.
  • Water is essential for the survival of life.
  • Water provides shelter to the large variety of plants and animals.
  • Plants use water for preparing food.
  • Water is essential for germination of seeds and their growth.
  Uses of Water Water is used for different purposes in our day to day life
  • Water is used for drinking, bathing, cooking and cleaning clothes.
  • Water is used for irrigation in agriculture.
  • Water is used in the industries for the production of various substances.
  • Water is used for the production of electricity.
  States of Water Water is found on earth in all the three states.   Solid: Snow is the solid state of water. When water is cooled, it is converted into ice. This process is known as freezing or solidification.   Liquid: When ice is heated, it is converted into water. This process is known as melting. Condensation is the process by which water vapor cooled down to convert into water.   Gas: Water vapor is gaseous state of water. When liquid water is heated, it gets converted into water vapor. This process is known as evaporation.   Water Cycle The continuous circulation of water from the earth's surface to atmosphere and from the atmosphere back to the earth is called water cycle.     Due to sunlight water from the different sources converts into water vapor. These water vapors rise up in the atmosphere and condense to water drops forming cloud. Then they return back to the surface of earth in the form of rain.   Sources of Water Oceans, seas, lakes, rivers, ponds, rainwater and ground water are the sources of water.   Rain Water: Rainwater is the purest form of water. It collects on the earth in the form of surface water and underground water.   Surface Water: Water present on the surface of the earth in the form of oceans, seas, rivers, lakes, ponds and streams is called surface water. Ocean contains almost 97% of water present on the earth. But it is saline therefore it is unfit for drinking. Underground Water: Some of the rainwater seeps through the soil and gathers in the non-porous rocks below. This water is known as underground water.   Conservation of Water As we have studied earlier water is very important for us. So we must conserve water whenever it is possible. Some ways of water conservation are:

  Number System and Its Operations   Numbers are the symbolic representation of counted objects. There are infinite counting numbers from 1. Some are divisible by another whereas some are not divisible. Numbers are differentiated according to their divisibility and factors. A numeral system is a writing system for expressing numbers. The most commonly used system of numerals is Hindu-Arabic numeral system. In this chapter, we will learn about various numeral systems, types of numbers and operation on numbers.   Indian or Hindu-Arabic Number System This number system was introduced by Indians, and is therefore, called Indian Number System. In this number system 10 is considered as the base. 10 ones = 10, 10 tens = 1 hundred, 10 hundreds = 1 thousand Hindu - Arabic number system is based on the place value of digits in number.   Indian Place Value Chart  
Crores Ten Lakhs Lakhs Ten Thousands Thousands Hundreds Tens Ones
    2 9 8 more...
  Fraction and Decimals   Fraction Fraction is a method for representing the parts of a whole number. An orange is divided into two equal parts and so the first part of orange is half of the whole orange and represented by \[\frac{1}{2}\] of the orange.   Types of Fractions   Proper Fractions A fraction whose numerator is less than denominator is called a proper fraction. \[\frac{3}{5}\]’ \[\frac{1}{2}\]’ \[\frac{7}{9}\] are Proper fractions.   Improper Fractions A fraction is called improper fraction even if:
  • It has smaller denominator than numerator
  • It has equal numerator and denominator
\[\frac{6}{5},\,\,\frac{5}{2},\,\,\frac{109}{34},\,\,\frac{6}{6}\]   Simplest form of a Fraction A fraction is said to be in the simplest or lowest form if its numerator and denominator have no common factor except 1.   Mixed Fractions Combination of a proper fraction and a whole number is called mixed fraction. Every mixed fraction has a whole and a fractional part.   Like and Unlike Fractions When two or more fractions have same denominator then they are called like fractions whereas unlike fractions do not have equal denominators.   Equivalent Fractions Two fractions are said to be equivalent if they are equal to each other. Two equivalent fractions may have a different numerator and a different denominator.   Example: Convert \[\frac{11}{2}\] into a mixed fraction.   (a) \[5\frac{1}{2}\]                                 (b) \[3\frac{1}{2}\] (c) \[\frac{1}{2}\]                                   (d) All the above (e) None of these Answer (a)   Example: \[\frac{5}{7},\,\frac{1}{2},\,\frac{2}{3}\]are: (a) like fractions              (b)  unlike fractions (c) equivalent fractions     (d) Mixed fractions (e) None of these Answer (b)   Operations on Fractions   Addition of Like Fractions Addition of like fractions is the addition of their numerators and common denominator is the denominator of the resulting fraction.   Addition of numerators Hence, the sum of like fractions =\[\frac{\text{Addition}\,\text{of}\,\text{numerators}}{\text{Common}\,\text{denominator}}\] Subtraction of Like Fractions Subtraction of like fractions is same as its addition except that addition is converted into subtraction. Let two like fractions are \[\frac{567}{456}\text{and}\,\frac{4546}{456}\] Their subtraction=\[\frac{\text{Subtraction}\,\text{of}\,\text{its}\,\text{numerators}}{\text{Common}\,\text{denominator}}\]   Multiplication of Fractions The following are the steps to perform the multiplication of like fractions: Step 1: Multiply the numerators and multiply the denominators. Step 2: Write the answer in lowest form.   or, Product of fractions= \[\frac{\text{Product}\,\text{of}\,\text{numerators}}{\text{Product}\,\text{of}\,\text{denominators}}\]   Division of Fractions Division of fractions is multiplication of the dividend by reciprocal of the divisor.   Example: Evaluate: \[\left\{ \left( \frac{3}{5}-\frac{7}{11}\times \frac{1}{2} \right) \right\}+\frac{9}{121}\] (a) \[\frac{3}{121}\]                               (b) \[\frac{43}{121}\] (c) \[\frac{431}{1210}\]                          (d) All the above (e) None of these Answer (c)   Explanation:   \[\left\{ \left( \frac{3}{5}-\frac{7}{11}\times \frac{1}{2} \right) \right\}+\frac{9}{121}=\frac{3}{5}-\frac{7}{22}+\frac{9}{121}\] \[=\frac{726-385+90}{1210}\] \[=\frac{431}{1210}\]   Example: What should be divided by \[\frac{\text{6}}{\text{11}\,}\,\text{to}\,\text{get}\,\frac{\text{3}}{\text{5}}\]?   (a) \[\frac{18}{55}\]                  (b) \[\frac{8}{55}\]  (c) \[\frac{55}{18}\]                  (d) \[\frac{30}{33}\]  (e) None of these             Answer (a) Explanation: Required number =\[\frac{6}{11}\times \frac{3}{5}=\frac{18}{55}\] Decimal Digits of decimal number are separated by a dot (.) called decimal point. Digits at the left from the dot (decimal) are called whole part and digits at the right side are called decimal part of the decimal number.   Place more...

  LCM and HCF   LCM (Least Common Multiple) LCM of two or more numbers is their least common multiple. LCM of 4 and 6 is 12, it means, 12 is the least common multiple of 4 and 6, therefore, 12 is exactly divisible by each of 4 and 6.   LCM by Prime Factorization Method The following steps are used to determine the LCM of two or more numbers by prime factorisation method: Step 1: Find the prime factors of each number. Step 2: Product of highest power of prime factors is their LCM.   LCM by Division Method The following steps are used to determine the LCM of two or more numbers by division method: Step 1: Numbers are arranged or separated in a row by commas. Step 2: Find the number which divides exactly atleast two of the given numbers. Step 3: Follow step 2 till there are no numbers (atleast two) divisible by any number. Step 4: LCM is the product of all divisors and indivisible numbers.   Example: Find the least number which is exactly divisible by each of 28 and 42. (a) 64                            (b) 84 (c) 52                            (d) All of these (e) None of these Answer (b)   Explanation: \[28=2\times 2\times 7,\,\,42=2\times 3\times 7\]            LCM =\[2\times 2\times 3\times 7=84\]   HCF (Highest Common Factor) Highest Common Factor is also called Greatest Common Measure (GCM) or Greatest Common Divisor (GCD). H.C.F of two or more numbers is the greatest number which exactly divides each of the numbers.   HCF by Prime Factorization Method The HCF of two or more numbers is obtained by the following steps: Step 1: Find the prime factors of each of the given number. Step 2: Find the common prime factors from prime factors of all the given numbers. Step 3: The product of the common prime factors is their HCF.   HCF by Continued Division Method The HCF of two or more numbers can also be obtained by continued division method. The greatest number is considered as dividend and smallest number as divisor.   Follow the following steps to perform the HCF of the given numbers: Step 1: Divide the greatest number by smallest. Step 2: If remainder is zero, then divisor is the HCF of the given number. Step 3: If remainder is not zero then, divide again by considering divisor as new dividend and remainder as new divisor till remainder becomes zero. Step 4: The HCF of the numbers is last divisor which gives zero remainder.   HCF of more than two Numbers The HCF of more than two numbers is the HCF of resulting HCF of two numbers with third number. Therefore, HCF of more than two numbers is obtained by finding the HCF of two numbers with third, fourth and so on.   HCF of Larger Numbers The HCF of smaller number (One or two digit numbers) is simply obtained by division but division of larger numbers take more more...

  Ratio and Proportion   Ratio Ratio of two quantities is the comparison of the given quantities. Ratio is widely used for comparison of two quantities in such a way that one quantity is how much increased or decreased by the other quantity.   For example, Peter has 20 litres of milk but John has 5 litres, the comparison of the quantities is said to be, Peter has 15 litres more milk than John, but by division of both the quantity, it is said that Peter has, \[\frac{20}{5}=4\] times of milk than John. It can be expressed in the ratio form as\[4:1\]   Note: In the ratio\[a:b\]\[(b\ne 0)\], the quantities a and b are called the terms of the ratio and the first term (ie. a) is called antecedent and the second term (ie. b) is called consequent.   Simplest form of a Ratio If the common factor of antecedent and consequent in a ratio is 1 then it is called in its simplest form.   Comparison of Ratio Comparison of the given ratios are compared by first converting them into like fractions, for example to compare \[5:6,\text{ }8:13\text{ }and\text{ }9:16\]first convert them into the fractional form i.e. \[\frac{5}{6},\frac{8}{13},\frac{9}{16}\]. The LCM of denominators of the fractions\[=2\times 3\times 13\times 8=624\] Now, make denominators of every fraction to 624 by multiplying with the same number to both numerator and denominator of each fraction. Hence,\[\frac{5}{6}\times \frac{104}{104}=\]\[\frac{520}{624},\frac{8}{13}\times \frac{48}{48}\]\[=\frac{384}{624}\]and\[\frac{9}{16}\times \frac{39}{39}\]\[=\frac{351}{624}\].Equivalent fractions of the given fractions are \[\frac{520}{624},\frac{384}{624},\frac{351}{624}\]. We know that the greater fraction has greater numerator, therefore the ascending order of the fractions are, \[\frac{351}{624}<\frac{384}{624}<\frac{520}{624}\] or \[\frac{9}{16}<\frac{8}{13}<\frac{5}{6}\] or \[9:16<8:13<5:6\], thus the smallest ratio among the given ratio is \[9:16\]and greatest ratio is\[5:6\].   Equivalent Ratio The equivalent ratio of a given ratio is obtained by multiplying or dividing the antecedent and consequent of the ratio by the same number. The equivalent ratio of \[\text{a}\,\,\text{:}\,\,\text{b}\] is \[\text{a}\,\times \,\text{q}\,\,\text{:}\,\,\text{b}\,\times \,\text{q}\]whereas, a, b, q are natural numbers and q is greater than 1.   Hence, the equivalent ratios of \[5:8\]are, \[\frac{5}{8}\times \frac{2}{2}=\frac{10}{16}\] or\[10:16\], \[\frac{5}{8}\times \frac{3}{3}=\frac{15}{24}\] or\[15:24\], \[\frac{5}{8}\times \frac{12}{12}=\frac{60}{96}\] or\[60:96\].   Example: Mapped distance between two points on a map is 9 cm. Find the ratio of actual as well as mapped distance if 1 cm = 100 m. (a) \[10000:1\]                (b) \[375:1\]         (c) \[23:56\]                    (d) \[200:1\] (e) None of these Answer (a)   Explanation: Required ratio =\[900\times 100:9=\] \[90000:9=10000:1\]   Example: Consumption of milk in a day is 6 litre. Find the ratio of Consumption of milk in month of April and quantity of milk in a day? (a) \[99:2\]                     (b) \[30:1\]         (c) \[123:3\]                    (d) \[47:3\] (e) None of these Answer (b) Explanation: Required ratio \[=30\times 6:6=30:1\]   Proportion The equality of two ratios is called proportion. If a cake is distributed among eight boys and each boy gets equal part of the cake then cake is said to be distributed in proportion. The simplest form of ratio \[12:96\]is \[1:8\]and\[19:152\]is \[1:8\]therefore, \[12:96\]and \[19:152\] are in proportion and written as \[12:96::19:152\]or more...

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