Mental Arithmetic : Able to add and subtract multiples of 10 and 100 mentally.

__Mental
Arithmetic__

__Able to add and
subtract multiples of 10 and 100 mentally.__

Multiples of 10 and 100 are useful in counting
large number of items and objects (including money).

**Multiples of 10**

**10, 20, 30, 40, 50**** ****.**** ****.**** ****..**

__Adding with
multiples of 10__

Here, one’s place didn’t change,
when they are added to zero and hundreds Place also didn’t change, only the
tens place got changed.

i) 2 + 1 = 3

ii) 4 + 1 = 5

Now we add the following

**EXAMPLE 1**

Add 374 + 10

4 + 0 = 4

7 + 1 = 8

Therefore 374 + 10 = 384

**EXAMPLE 2**

Add 286 + 30

8 + 3 = 11

Here, 11 has two digits, in this
keep 1 in the tens place, take the other 1 and add with the hundreds place
digit.

Therefore 286 + 30 = 316

__Adding with
multiples of 100__

Here, one's place and ten's place
didn't change, when they are added to zero but in the hundreds place it is
changed.

**EXAMPLE 3**

Add 682 + 100

2 + 0 = 2

8 + 0 = 8

6 + 1 = 7

∴ 682 + 100 = 782

**EXAMPLE 4**

Add 835 with 100

8 + 1 = 9

∴ 835 + 100 = 935

__Subtracting by
multiples of 10__

Follow the same procedure of
addition for subtraction also, instead of adding the numbers, subtract the
numbers in the circle.

**EXAMPLE 5**

Subtract 10 from 625

5 – 0 = 5

2 – 1 = 1

∴ 625 – 10 = 615

**EXAMPLE 6**

Subtract 50 from 981

8 – 5 = 3

∴ 981 – 50 = 931

__Subtracting by
multiples of 100__

**EXAMPLE 7**

Subtract 400 from 546

5 – 4 = 1

∴ 546 – 400 = 146

Tags : Numbers | Term 3 Chapter 2 | 4th Maths , 4th Maths : Term 3 Unit 2 : Numbers

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4th Maths : Term 3 Unit 2 : Numbers : Mental Arithmetic: add and subtract multiples of 10 and 100 mentally | Numbers | Term 3 Chapter 2 | 4th Maths

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