



 
Andrew, The volume of a pyramid is (1/3)Ah, where A is the area of the base and h is the height. A frustum is just the lower part (i.e. not including the tip). So the volume of the frustum is the same as the volume of the fullsize pyramid MINUS the volume of the "missing" pyramid on top. So you need to find out how tall the pyramid would be if it weren't chopped off. You can see that half the lengths of the sides are 2.5 inches and 1.5 inches. It takes 12 inches of vertical space to go from 2.5 to 1.5, so how many inches of vertical space does it take to go from 2.5 all the way to 0 (the point of the pyramid)? Knowing this, you can calculate the two pyramid volumes, subtract and get one of the answers in the list. Cheers,  


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