Answer: radius r = 2 inches
height h = 6 inches
Step-by-step explanation:
Given;
Volume V = 24πin3
Volume of a cylinder is given by
V = πr^2h
h = V/πr^2. ....1
Where, h = height and r = radius of cylinder
For the surface area of the cylinder with open top. we have,
S = 2πrh + πr^2
For the cost of materials used, let k represent the cost of materials used for the body of the cylinder.
Then, for the bottom will be 3k
Total cost will be represented by C, which gives
C = 2πrhk + 3πr^2k. .....2
Substituting eqn 1 to 2, we have;
C = 2πrVk/πr^2 + 3πr^2k
C = 2Vk/r + 3πr^2k
The material cost is minimum at dC/dr = 0
dC/dr = -2Vk/r^2 + 6πrk =0
6πrk = 2Vk/r^2
r^3 = 2V/6π
r = (2×24π/6π)^-3
r = (8)^-3
r = 2
Substituting r = 2 into eqn1
h = 24π/π(2^2)
h = 24/4 = 6
h = 6
