½Bh = V
where B = b × htri (triangle base × triangle height) and h = pyramid height — then multiply by ⅓ for the pyramid
Full formula: V = ⅓ × ½ × b × htri × H = ⅓ × B × H
b=8 ft, h=5 ft, H=9 ft
V=60 ft³, b=8 ft, h=5 ft