Emil is cutting a 72-inch-long board and a 54 in long board into shelving. He wants to make as many shelves as he can while using up all the wood. What is the longest possible length of the shelves?

The longest possible length of the shelves =  18 inches

Step-by-step explanation:

Given: Lengths of two boards are  72-inches and 54 inches.

To make as many shelves as he can while using up all the wood we will find the longest possible length of the shelves = HCF ( 72, 54)

72 = 2 x 2 x 2 x 3 x 3

54 = 2 x 3 x 3 x 3

HCF(72,54) = 2 x 3 x 3 = 18

Hence, the longest possible length of the shelves =  18 inches