Answer: 80 cubic meters (choice B)
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Explanation:
The floor of the pyramid is a pentagon made of five congruent isosceles triangles as shown in the diagram below. Each triangle has a base of 6 meters and height 2 meters. The base and height are always perpendicular.
Each triangle mentioned therefore has area base*height/2 = 6*2/2 = 12/2 = 6 square meters. Five such triangles results in a total area of 6*5 = 30 square meters. This is the area of the pentagonal floor.
We'll multiply this area by the height of the pyramid (8 meters) and then take 1/3 of this to get the pyramid's volume
volume = (1/3)*(area of floor)*(height of pyramid)
volume = (1/3)*(30)*(8)
volume = 10*8
volume = 80 cubic meters
