Answer:
1/8 ft³
Explanation:
Apparently cubic blocks that are 1/5 of 2 1/2 ft on a side are used to fill the cube that is 2 1/2 ft on a side. Then each edge of the block is ...
(1/5) × (5/2 ft) = 1/2 ft
The volume of the block is the cube of that:
(1/2 ft)³ = 1/8 ft³