  Mental Maths

• Mental addition tricks help us to do addition faster and easily.

We will learn some easy methods to do addition fast. Addition of 1-digit and 2-digit numbers

• We use number bonds of 10. • In the above example, we know that the number bond of
10 as 7 + 3 = 10
• So, we take away 3 from 29 and add it to 7.
• 29 becomes 26. We can split it as 20 + 6.
• Now adding 10 + 20 + 6, we get 36.

• Split two-digit numbers into tens and ones. • In the above example, we can split the number 13 as one 10 and 3 ones.
• Then we can add 5 + 3 = 8.
• Now adding this 8 to 10, we get 18.

• Add the Tens place numbers only. • In the above example, Ones place numbers are 0. We know that, 0 + 0 = 0. So, ones place number will be always 0.
• Then directly add tens place numbers here: 3 + 6 = 9
• We get sum as: 30 + 60 = 90
• Another method (Count forward by observing tens-place numbers)

• Between 30 and 60, the number 60 is greater.
• The number 30 has 3 at its Tens place. So, from 60 count 3 steps forward in the form of tens. • We add the numbers in the unit place and the numbers in the tens place separately. (Imagine numbers in column.) • In the above example, first we add Ones place digits. Remember this answer. This answer will be Ones place digit in the final answer.
• Then add Tens place digits. This answer will be the Tens place digit of our final answer.

Case 2: When we get sum of ones place digits as a 2-digit number

• If we get 2-digit number as the sum of ones place digits, add one to the tens column answer. • In the above example, first we add Ones place digits:
7 + 6 = 13.
The number 3 in this 13 is our ones place digit number in the answer and we hold 1.
• Then we add Tens place digit: 5 + 2 = 7
We add that 1 to 7: 1 + 7 = 8

• Split two-digit numbers into tens and ones. • In the above example, we split the number 23 as: 20 + 3
• And split the number 14 as 10 + 4
• Then add 1-digit numbers: 3 + 4 = 7
• Then it is easy to add: 20 + 10 + 7 = 37
• Addition by rounding off numbers into tens.

• Here we rounded off one addend. • In the above example, if we add 3 to 57, we get 60.
• So, we take away 3 from 38 and added it to 57.
• 57 became 60 and 38 became 35.
• By adding 60 and 35, we got 95.  • -