Current Affairs 3rd Class

Numbers    

• The number system contains ten digits 0,1,2,3,4,5,6,7,8,9.

Largest and smallest numbers:

• The smallest one digit number is 1.
• The largest one digit number is 9.

 

• The smallest two digit number is 10.
• The largest two digit number is 99.
• The smallest three digit number is 100.
• The largest three digit number is 999.
  • 10 Ones = 1 Ten
  • 10 Tens = 1 Hundred
• 10 Hundreds = 1 Thousand

Place Value of each digit in a number: In a four digit number, there are four places named: Ones place. Tens place. Hundreds place and Thousands place. Ex:     Ascending Order of numbers: Arranging numbers from the least number to the largest number is called Ascending Order. Ex: 13, 67, 132, 168 are in ascending order Descending Order of numbers: Arranging numbers from the largest number to the least number is called Descending Order. Ex: 168, 132, 67, 13 are in descending order. Symbols used for comparison of two numbers: This is the "equal to” sign. When we use it between two numbers, it means that the numbers on both sides of the sign have the same value. Ex: 53 = 53 This is the "greater than" sign. It is placed between two numbers in such a way that the open side is towards the bigger number. Ex: 43 > 34 This is the “less than" sign. It is placed between two numbers in such a way that the closed side is towards the smaller number. Ex: 57 < 69 Rules for comparison of numbers: Rule 1: A numeral containing more digits is greater. Ex: 163 > 35 Rule 2: If two numerals contain the same number of digits, the numeral having greater digit at the left most place will be greater.   Rule 3: If the left most digits are also the same, we go to next digit from left and compare.   Successor of a numeral: Successor of a particular numeral comes just after that numeral. So, we can find out the successor of a numeral by adding 1 to the given numeral. Ex : The successor of 99 is 99 + 1 or 100. Predecessor of a numeral: Predecessor of a particular numeral comes just before that numeral. So, we can find out the predecessor of a numeral by subtracting 1 from more...

Addition and Subtraction   Concept of Zero:

• Zero added to any number is equal to the number itself.

Example: 243 + 0 = 243 Addition:

• While adding, if we change the order of the numbers, the result will be the same.
• Addition of 3-digit numbers is done by arranging the digits of ones, tens and hundreds in their proper place.
• First we add ones, then tens and then hundreds.

Addition of 3-digit numbers without carrying: Example: Add 376 and 213 Solution: Step- 1: Arrange the numbers according to their proper place values.   Step-2: Add the ONES first, then the TENs and finally the HUNDREDS.      

• Addition of3-digit numbers with carrying :

Example: Add 498 and 376 Solution: Step-1: Arrange the digits of the numerals in proper places.  

• Step -2: Add ones

8+6=14 14 ones = 1 ten + 4 ones 1 ten is carried to tens column. 4 is written in ones place. Step - 3: Add tens 1 + 9 + 7 = 17 17 tens = I hundred + 7 tens 1 hundred is carried to hundreds column. 7 is written in tens place.   Step - 4: Add Hundreds 1+4+3=8 8 is written in Hundreds place.   Subtraction:

• Zero subtracted from any number is equal to the number itself.
• First we subtract ones, then tens and then hundreds.

Subtraction of3-digitnumbers without borrowing: Ex: Subtract 652 from 956 Step - 1: Arrange the numbers according to their proper place values. Step-2: Subtract ONES first, then the TENS and finally the HUNDREDS.  

• Subtraction of 3 - digit numbers with borrowing:

Ex : Subtract 652 from 831. Step-1: Arrange the numbers according to their proper place values.     Step - 2: Subtract ONES 1 – 2 = ? We can't subtract 2 from 1.      more...

Multiplication   Multiplication:

• Multiplication is a repeated addition.
• The number to be multiplied is called the MULTIPLICAND.
• The number by which we multiply is called the MULTIPLIER.
• The answer is called the PRODUCT.

  Note: 

• The product of a number and zero is zero.
• The product of a number and is the number itself.
• When the order of the numbers is changed, the product remains the same.

  Multiplication of 3 - digit numbers by 1-digit number: Ex: Multiply 498 by 3.  

• Step - 1: Multiply 8 ones by 3.

8 ones x 3 = 24 ones = 2 tens + 4 ones write 4 in the ones place. Carry 2 tens to the tens place. Step - 2: Multiply 9 tens by 3. 9 tens \[\times \] 3 = 27 tens = 20 tens + 7 tens = 2 hundreds + 7 tens Carry 2 hundreds to the hundreds place. Add the carried 2 tens to 7 tens. So 7 tens + 2 tens = 9 tens, write 9 in the tens place   Step - 3: Multiply 4 hundreds by 3. hundreds x 3 = 12 hundreds. Add the carried 2 hundreds to 12 hundreds. So, 12 hundreds + 2 hundreds = 14 hundreds, write 14 in hundreds place   Multiplication by TENS and HUNDREDS: 5 \[\times \] 10 = 5 \[\times \]1 ten = 5 tens = 50 7\[\times \] 30 = 7 \[\times \] 3 tens = 21 tens = 210 15 x 60 = 15 \[\times \] 6 tens = 90 tens = 900 8\[\times \]100=8\[\times \] 1 hundred = 8 hundreds = 800 9 \[\times \] 400 = 9 \[\times \] 4 hundreds = 36 hundreds = 3600 Multiplication by 2-digit numbers: Ex: Multiply 36 by 25    

Division   Division:

• Division is a process of dividing into groups. It is also considered as a process of repeated subtraction.

Equal - sharing: Ex : 1 have 12 apples with me and I want to distribute them equally among 3 boys. How many apples will each boy get? Step - 1: Give 1 apple to each boy.   we have, 12-3 =9 apples left.   Step - 2: Again give 1 apple to each boy.   we have, 9-3=6 apples left. Step - 3: Give 1 more apple to each boy   We have, 6-3=3 apples left. Step - 4: Again give 1 more apple to each boy.     We have, 3-3=0. Each boy has got 4 apples and no apple is left. We observed that 12 apples have been distributed among 3 boys. Each boy got 4 apples. Thus 12- 3=4       Grouping: Ex: 9 balls are to be distributed among some boys. Each boy should get 3 balls. How many boys are there? Step -1: Give 3 balls to one boy   We have, 9 - 3=6 balls left. Step - 2: Give 3 balls to the next boy. We have, 6 - 3=3 balls left Step - 3: Give 3 balls to the next boy. We have, 3 - 3 =0 No balls left. We observed that, Three boys got the balls.     Thus, 9 – 3 = 3 Multiplication and Division facts:   Basic terms used in division:

• Dividend: It is the number we divide.
• Divisor: It is the number with which we divide.
• Quotient: It is the result obtained on division.

• Remainder: It is the number left undivided.

 

• Dividend = divisor x quotient + remainder
• In division, the remainder has to be either "0" or less than divisor.
• If we divide a number by the number itself, then the quotient is 1.
• If we divide a number by 1, the quotient is the same as the dividend.

 

• Long division:

Ex: Divide 93 by 4 using long division. Step - 1: Arrange the numbers in the following more...

Fraction Fractions:

• A fraction represents the part of a whole.
• The number above the bar is called NUMERATOR and the number below the bar is called

\[\operatorname{ex}:\frac{3}{4}\]

• To get equivalent fractions for a given fraction multiply its numerator and denominator by the same number.
• Fractions having equal denominators are called LIKE fractions.
• Fractions with unequal denominators are called UNLIKE fractions.
• If two fractions have the same denominator, then the fraction with greater numerator is greater fraction.

 

• If two fractions have the same numerator, then the fraction with smaller denominator is greater fraction.

\[\operatorname{Ex}:\frac{5}{9}>\frac{5}{11}\]

• Sum of fractions having same denominator

\[=\frac{Sum\text{ }of\text{ }Numerators}{Denominator}\]  

• Difference between two fractions having same denominator

\[=~\frac{Difference between Numerators}{Denominator}\]      

Money    

• In India, the unit of money is RUPEE.

 

• 1 Rupee = 100 paise

 

• Symbol for Rupee is Re. and Rupees is Rs.

 

• Symbol for paise is P.

 

• The figures on the left of dot (.) denote Rupees, and the figures on the right of dot (.) denote paise.

 

• To convert rupees to paise, multiply by 100. Ex: Rs. 11.50 = 11. 50 \[\times \]100 = 1150 P

 

• To convert paise to rupees, divide by 100. Ex: 1250 P = 1250 - 100 = Rs. 12.50\

 

• 100 paise make 1 Rupee. 50 paise make half Rupee.

 

Time   Clocks:

• A clock has two hands : (i) long hand and (ii) short hand

 

• The long hand is called minute hand and the short hand is called hour hand.

 

• Some clocks have a third hand called second hand. It moves much faster than the other two hands

 

• The dial of the clock is divided into 12 equal divisions marked as 1,2,3,4,5,6,7,8,9,10,11 and 12

 

• 1 hour = 60 minutes    I minute = 60 seconds

 

• \[\therefore \]1 hour = 60 \[\times \] 60 = 3600 seconds

 

• The hour hand takes 12 hours to complete one round.

 

• The minute hand takes 1 hour to complete one round.

  Some conversions:

• 1 day = 24 hours; 1 week = 7 days; 1 month = 4 weeks; 1 year = 12 months 1 year = 52 weeks; 1 year = 365 days

 

• The time from 12 midnight to 12 noon is noted as A.M. (Anti Meridian) and the time form

12 noon to 12 midnight as P.M. 4Post Meridian).          

Measurement  

• Non-standard Units of Length:
  • Length \[\to \] fingers, hand span, cubit, pace etc.

 

• Standard Units of Length:
• Meter is a standard unit for measuring length.
• 1 meter = 10 decimetres
• 1 decimeter = 10 centimetres
• 1 metre = 100 centimetres

 

• Non-standard Units for Mass:
  • Mass \[\to \] marbles, stones, beads etc.

 

• Standard Units for Mass:
  • Kilogram is a standard unit of mass.
  • 1 kilogram = 1000 grams

 

• Non - Standard Units of Capacity:
  • Capacity \[\to \] Cup, bottle, tumbler etc.

 

• Standard Units of Capacity:
• Liter is a standard unit of capacity.

1 liter = 1000 milliliters              

Shapes   Basic shapes:

• 2 – dimensional shapes:

   

• 3 - dimensional shapes:

         Closed and Open figures:  

• Closed figures:

 

• Open figures:

    Description of some basic shapes:

• Square       Rectangle

      It has four sides and four corners.  All its sides are of same length.   It has four sides and four corners. The opposite sides of a rectangle are having same length.  

• Triangle Cuboid

     

• Cube                Cylinder

        It has 6 flat faces and 12 straight edges.  It has 3 faces\[\to \] 1 curved face and 2 flat faces.. It has 2 cured edges.    

• Cone

  It has 2 faces \[\to \]  1 curved face and 1 flat face. It has 1curued edge.                

Pictographs   Pictograph:

• A pictograph uses pictures or symbols to represent an assigned amount of data.

 

• A pictorial representation of data is a useful method to represent data attractively.

 

• Numerical data when presented through pictures is called pictorial representation.

 

• Pictographs are also called as pictograms.