A mental math trick — addition with nine and eight

This neat and easy "trick" allows you to add 9 or 8 to any number with ease!

For example, to solve 9 + 7, imagine that 9 wants to be 10, so it gets "one" from the seven, leaving seven to become only six. So the addition 9 + 7 is changed to the sum 10 + 6 which is super easy to solve.

We can also use a similar strategy in sums with 8. For example to solve 8 + 5, imagine that 8 wants to be 10, so it gets two from the 5, which then becomes only 3. So the sum 8 + 5 becomes 10 + 3, which is an easy sum to solve.

First and second graders can use these mental math techniques to help their load of memorization of addition facts.

This same "trick" or thought pattern also works with two-digit numbers ending in 9, three-digit numbers ending in 99, and so on.

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See also

Add a 2-digit number and a single-digit number mentally - no regrouping — video lesson

Math Mammoth Grade 1 curriculum

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