use compatible numbers to estimate the product of 2/3 X 22

Question

This is a fraction assignment. The directions say to use compatible numbers to estimate the product. The problems are:

1.)   2/3 X 22

2.)   3/5 X 32

Answer 1

1) 21 is compatible with 22 and it means we can easily calculate 2/3 because 3 goes into 21. 2/3 of 21=14, so 2/3 of 22 must be close to this. The true answer is 14 2/3, only two thirds bigger than the estimated 14.

2) 3/5 is close to 1/2 so since half of 32 is 16, this must be close to the true answer, which is 19.2. We could also use 30 instead of 32, because 5 goes into 30 6 times, so 3/5 is 3*6=18. This is a better estimate, because it's closer to 19.2.