Mental Maths
Mental Addition Strategies
What is mental addition?
- Mental addition means to do the addition of numbers in your head mentally without using a pen paper or any machine.
- 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
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Addition by making 10.
- 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.
- We use number bonds of 10.
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Addition by splitting
- 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.
- Split two-digit numbers into tens and ones.
Addition of 2-digit numbers
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Addition of tens numbers.
- 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
- Add the Tens place numbers only.
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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.
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Addition by columns.
- 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
- We add the numbers in the unit place and the numbers in the tens place separately. (Imagine numbers
in column.)
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Addition by splitting
- 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
- Split two-digit numbers into tens and ones.
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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.
- Here we rounded off one addend.