Mental Maths Addition

1. Add 4 + 8

Solution:   

4 + 8 = 8 + 4

4 + 8 = 8 + I, I, I, I

         = 8, 9, 10, 11, 12

Therefore, 4 + 8 = 8 + 4 = 12

Instead of adding 8 to 4, 4 is added to 8 as 4 + 8 = 8 + 4.

While calculating mentally, we go to count four numbers ahead.

2. Add 5 + 17

Solution:

We know that, 5 + 17 = 17 + 5

So, 17 + (I, I, I, I, I)

= 17, 18, 19, 20, 21, 22

Therefore, 5 + 17 = 17 + 5 = 22

Instead of adding 17 to 5, 5 is added to 17 as 5 + 17 = 17 + 5.

While calculating mentally, we go to count five numbers ahead.

3. Add 8 + 5 + 3

Solution:

8 + 5 + 3 = 8 + 3 + 5

= 11 + 5

= 16

Therefore, 8 + 5 + 3 = 8 + 3 + 5 = 16

Instead of adding 8 + 5 + 3 we arrange the numbers as 8 + 3 + 5 then, 8 + 3 = 11 and 11 + 5 = 16

4. Add 70 + 40

Solution:

70 + 40

= 110

Only the digits at ten’s place are added, if the numbers are the multiples of 10.

Zero is placed at one’s place in the addition result.

5. Add 60 + 35

Solution:

60 + 35

= 60 + 30 + 05

= 90 + 05

= 95

Therefore, 60 + 35 = 95

Numbers are split in tens and ones.

Sum of tens and sum of ones are added.

6. Add 67 + 43

Solution:

67 + 43

= (60 + 7) + (40 + 3)

= 60 + 40 + 7 + 3

= 100 + 10

= 110

Numbers are split in tens and ones and then do addition.

      or,
                  67

                  43
                  10 (7 + 3)

                 100 (60 + 40)
                 110

Sum of ones and sum of tens both are added.