Here is a number sense trick to help you calculate addition using mental math.

We want to find the sum of 9 + 8 + 7. Using our number sense, we turn to “friendly numbers” such as 10 or multiples of 10, to help make this math easier to work with.

The word quarter means “4 parts the same,” “four equal parts”.

To find a quarter of any amount, cut the whole into “4 parts the same” and take any one part. The trick to doing this easily is to “cut it in half and then cut the half in half and take any piece.” A quarter also means “half-of-a-half.”

To find one quarter of 8 we cut the whole of 8 circles into “4 parts the same” by cutting the whole in half, and then the half in half.

Recall that half means “2 parts the same,” “two equal parts.”

Half of 6 circles is 3 because we cut the whole into “2 parts the same” and take one part.

To find half of 7, we bring in one more circle and cut our new whole into “2 parts the same.” Taking either part we have:

half of 7 = .