SOLUTION: A water tank is in the shape of a circular cylinder with the height of 20 feet and a volume of 320 pie cubic feet. What is the diameter, in feet, of the water tank? A. 16 B. 10

Algebra ->  Volume -> SOLUTION: A water tank is in the shape of a circular cylinder with the height of 20 feet and a volume of 320 pie cubic feet. What is the diameter, in feet, of the water tank? A. 16 B. 10      Log On


   

Question 1139265: A water tank is in the shape of a circular cylinder with the height of 20 feet and a volume of 320 pie cubic feet. What is the diameter, in feet, of the water tank?
A. 16
B. 10
C. 8
D. 4
Why is it that answer?
Found 2 solutions by math_helper, MathLover1:
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
+V%5Bcyl%5D+=+%28pi%29r%5E2h+
h=20
V=320%2A%28pi%29
Solving for 2r (= diameter): ft

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
a volume of circular cylinder is:
V=pi%2Ar%5E2h
given:
V=320pi%2Aft%5E3
h=20ft
320pi%2Aft%5E3=pi%2Ar%5E2%2A20ft
%28320pi%2Aft%5E3%29%2F%28pi%2A20ft%29=r%5E2
r%5E2=16ft%5E2
r=4ft
=> then diameter of the water tank is: d=2r=>d=8ft
answer: C. 8
Why is it that answer? because, solving equation above, we got radius and diameter is two times greater