f) 65 + 7 =
The answers are:
a) 34
b) 55
c) 81
d) 64
e) 45
f) 72
You don’t have to add and subtract the way you were taught at school. In fact, high maths achievers
usually use different methods to everyone else. That is what makes them high achievers — not their
superior brain.
How would you add 38? Add 40 and subtract 2.
So, how would you add the following?
a) 23 + 48 =
b) 126 + 39 =
c) 47 + 34 =
d) 424 + 28 =
For a), you would say 23 plus 50 is 73, minus 2 is 71.
For b), you would say 126 plus 40 is 166, minus 1 is 165.
For c), you would say 50 plus 34 is 84, minus 3 is 81.
And for d), you would say 424 plus 30 is 454, minus 2 is 452.
Did you find these easy to do in your head?
What if you have to add 31 to a number? You simply add 30, and then add the 1. To add 42 you add
40, and then add 2.
Test yourself
Try these:
a) 26 + 21 =
b) 43 + 32 =
c) 64 + 12 =
d) 56 + 41 =
The answers are:
a) 47
b) 75
c) 76
d) 97
You may have thought that all of those answers were obvious, but many people never try to calculate
these types of problems mentally.
Often you can round numbers off to the next hundred. How would you do the following problem in
your head?
You could say 2,351 plus 500 is 2,851 (300 + 500 = 800), minus 11 is 2,840.
Normally you would use a pen and paper to make the calculation, but when you see 489 as 11 less
than 500, the calculation becomes easy to do in your head.