V = 1/3 B * h
B = ???
h = 4 cm
V = 48 cm^3
48 = 1/3 * B * 4 Multiply both sides by 3
48 * 3 = B * 4
144 = B * 4 Divide by 4
144/4 = B
36 = B
Since the base is a square the area of the base = s^2
s^2 = 36
Sqrt(s^2) = sqrt(36)
s = 6 cm <<<<==== answer.