The bottom shape is a square prism with base edges of 5 feet and a height of 15 feet. what is the volume of the composite figure if the top shape is a right pyramid with a height of 3 feet? 375 ft3 225 ft3 25 ft3 400 ft3

The volume of the prism is
  V = Bh
where B is the area of the base, (5 ft)² = 25 ft², and h is the height, 15 ft.

The volume of the pyramid is
  V = (1/3)Bh
where B is the area of the base, 25 ft², and h is the height, 3 ft.

The total volume is the sum of these:
  V = Bh₁ + (1/3)bh₂
  V = B(h₁ + (1/3)h₂)
  V = (25 ft²)·(15 ft + (1/3)·(3 ft))
  V = (25 ft²)·(16 ft) = 400 ft³