Current Affairs 3rd Class

Category : 3rd Class

Number Sense and Numeration

Introduction

Everything is counted by numbers. Numbers are the symbolic representation of counted objects.

Types of Number

Natural Numbers

Counting numbers are known as natural numbers.

For example, natural numbers (N) = {1, 2, 3, 4, 5 .... to infinite}

Whole Numbers

Counting numbers including 0 are known as whole numbers.

For example, whole numbers (W) = {0, 1, 2, 3, 4 ..... to infinite}

Even Number

Numbers which are exactly divisible by 2 are called even numbers.

For example: {2, 4, 6, 8, etc.}

Odd Numbers

Numbers that are not exactly divisible by 2 and leaves remainder are called odd numbers.

For example: {1, 3, 5, 7 etc.}

Operations on Numbers

Place Value

Place value of digits of a number is their position in the number. For example, place value of 2 in 54276 is 200. Place value of 5 in 5674 is 5000.

Expanded form of numbers

Expanded form of every number is written according to the place value of digits. For example, expanded form of number\[56434=5\times 10000+6\times 1000+4\times 100+3\times 10+4\]

Face Value

Face value of every number is the number itself. For example, face value of 5 in numeral 4356 is 5 itself and face value of 4 in 4536 is 4.

Successor

Successor of every number is just after the number. For example/successor of 17 is 18. Successor of a number is obtained by adding 1 to the number.

Predecessor

Predecessor of every number is just before the number. For example, predecessor of 67 is 66. Predecessor of a number is obtained by subtracting 1 from the number.

Ascending Order

Arrangement of the numbers from smallest to greatest is called the ascending order of the numbers. For example, ascending order of 45, 67, 21, 34 is\[21<34<45<67\].

Descending Order

Descending order is the arrangement of numbers in decreasing order. For example, descending order of 50, 45, 23, 12, 22 is\[50>45>23>22>12\].

Rounding Counting Numbers Nearest to Ten

Rounding counting number 23763 to nearest 10 is 23760. So unit digit is mostly changed while rounding counting numbers to nearest ten. Sometimes, tens digit may also be changed. For example, rounding of 458 to nearest 10 is 460.

• Example

Arrange the following capacity of packing materials in ascending order.

Which one of the following is correct about their ascending order?

(a) \[Pouch<Tin<Gallon<Bottle\] 

(b) \[Bottle<Pouch<Tin<Gallon\]

(c) \[Tin<Gallon<Bottle<Pouch~\]

(d) All the above

(e) None of these

Answer (a)

Explanation: Since millilitres < centilitres < decilitres < litres and 1 centilitre =10 millilitres and 1 litre = 10 decilitres. Therefore, option (a) is correct.