Geometry
posted by Frank .
A sandpit in the shape of a rectangular prism has length 7 feet, width 5 feet, and height 1.75 feet. It is filled to the brim with sand. Joe puts this sand into a second sandpit having the same shape but a larger base. He needs 17.5 cubic feet of sand to fill the extra space inside the second sandpit.
If the height of the two sandpits is the same, what are the dimensions of the base of the second sandpit?
Answer
A.5 feet x 2 feet
B.10 feet x 7 feet
C.9 feet x 5 feet
D. 20 feet x 25 feet

The small pit used 35*1.75 ft^3 of sand
The large pit used all that plus an addition 17.5 = 10*1.75 ft^3
35*1.75
+10*1.75

45*1.75
Looks like (C) to me.