9/50 is about 10/50, or 2/10

7/15 is about 7.5/15 = 1/2 or 5/10

An estimate of the sum is (2+5)/10 = 7/10 = 0.7

97/150 ≈ 0.647, so our estimate was a little high. This is because the numbers we used in our estimate were both higher than the original number.

7/15 is about 7.5/15 = 1/2 or 5/10

An estimate of the sum is (2+5)/10 = 7/10 = 0.7

**The actual sum is (9*3+7*10)/150 = 97/150**97/150 ≈ 0.647, so our estimate was a little high. This is because the numbers we used in our estimate were both higher than the original number.