Lynne bought a bag of grapefruits, 1 5/8 pounds of apples and 2 3/16 pounds of bananas. The total weight was 7 1/2 pounds. How much did the bag of grapefruit weigh?

3 11/16 pounds

Step-by-step explanation:

The third item in the group had a weight that is the difference between the total and the sum of the two other items:

bag weight = (7 1/2) - ((1 5/8) + (2 3/16))

It can be convenient to use a common denominator of 16, so this is ...

bag weight = 7 8/16 - (1 10/16 + 2 3/16)

= 7 8/16 - (3 13/16)

= (7 - 3) + (8/16 - 13/16)

= 4 - 5/16

= 3 11/16

The weight of the bag of grapefruit was 3 11/16 pounds.