4) A 3cm*4cm*5cm rectangular metal block was put into a well that took the shape of a right circular cylinder. When the block was submerged, the water level in the container had increased by 0.5 centimeters. What is the base area of the well in square centimeters?
V prism = 3 * 4 * 5 = 60cm^3
V of cylinder without prism = pi * r^2 * h
V of cylinder with prism added = pi* r^2 (h + .5)
V of cylinder with added prism - V of cylinder without prism = volume of prism
[ pi * r^2*(h + 5cm)] - [ pi * r^2 * h] = 60 cm^3
pi^r^2 *h + pi*r^2 * .5cm - pi * r^2 * h = 60 cm^3
pi* r^2 * .5 cm = 60 cm^3
r^2 = 60cm^3 / [.5 cm pi]
r^2 = 120cm^2 / pi
pi * r^2 = 120 cm^2 = base area of well