Mental Subtraction Strategies
- Mental math is a skill that helps students to do math in their heads without using paper and pencil.
- Mental Math is useful in school and everyday life.
- It also helps to do calculations faster.
- The larger number is called the minuend.
- The smaller number is called the subtrahend.
- The resultant number is called the difference.
Method 1:(Add, and subtract)
- Express the subtrahend as the difference of the nearest hundred in a one/two-digit number.
- Then do the subtraction while adding the one/two-digit number with the minuend
Now, 189 = 200 – 11
So, 278 – 200 + 11 = 78 + 11 = 89
Method 2:(Split the Problems)
- The basic idea is to split the minuend and subtrahend into two or more numbers which are easier to work with.
- While splitting we will obviously take one number which is nearest to the hundred.
- 568 = (500 + 68)
329 = (300 + 29)
Now, 500 – 300 = 200
68 – 29 = 39
So, 200 + 39 = 239
Hence, 568 – 329 = 239
Method 3:(Nikhilam rule)
- Nikhilam rule says that “All from 9 and the last from 10.”
- That means all digits should be subtracted from 9 and the last digit should be subtracted from 10.
- After the subtraction, the difference should be added to the minuend.
- Deleting the left first digit of the sum of the minuend and the result, we get the final result of the subtraction.
- We need to subtract 123 from 9910 like the following way
- 897 – 250 =
We need to subtract 250 from 9100 like the below way