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Answer:
105
For the 4 triangular faces, find the area with 1/2 × base × height = 1/2 × 5 × 8 = 20
4 triangles -> 20 × 4 = 80
The area of the square base is 25
80 + 25 - 105
The Answer is 21 because 7 and 3 can go in it as well
A
The volume (V) of a pyramid is found using the formula
V = × area of base × height(h)
area of base = 9² = 81 ← area of a square, hence
324 = × 81 × h = 27h ( divide both sides by 27 )
h = = 12 → A