Mental Subtraction

Here We see Mental Subtraction.

To Subtract Mentally, try and round off the number you are subtracting and then correct the answer.

(i.e) To subtract 9, take 10 and add 1; To subtract 8, take 10 and add 2; and so on.
For example, 47 – 9 = ?

The easiest and fastest method is to subtract 10, (37) and add 1 (38).
So the answer is 47 – 9 = 38.

To Subtract 27 from 44. Take 30, (14) and add 3, answer is 17.

Similarly to subtract a number near 100, take 100 and add the remainder.

• Subtracting One Number Below a Hundreds Value from Another which is just Above the same Hundreds Number.

This is easy method for mental subtraction. For example 124 – 86 = ?

Here 86 is 14 lower than 100, 124 is 24 higher than 100. So Add 14 to 24 for an easy answer of 38.

The Same principle applies for numbers above and below 10. For example, 15 – 6 = ?
(i.e.) 5 + 4 = 9 answer.

Similarly this works for any three digit subtraction.

For example, 445 – 286 = ?

286 is 14 lower than 300, 445 is 145 higher than 300. So the answer is 145 + 14 = 159.

Try these for yourself by applying the above method :-

39 – 7 = ?
54 – 38 = ?
436 – 84 = ?
134 – 76 = ?
152 – 88 = ?
14 – 9 = ?
834 – 275 = ?


Yes, Hope You have done all the above very easily and quickly.