SOLUTION: I have a couple of problems that I am trying to help my daughter to understand but I admit it's been years and I can't remember how to do them so I am going to submit them one at a

Algebra ->  Volume -> SOLUTION: I have a couple of problems that I am trying to help my daughter to understand but I admit it's been years and I can't remember how to do them so I am going to submit them one at a      Log On


   

Question 140540: I have a couple of problems that I am trying to help my daughter to understand but I admit it's been years and I can't remember how to do them so I am going to submit them one at a time. I hope someone can help me help her. Here's the question: A cylinder has a volume of 85.6 cubic meters. If the radius is tripled and the height is doubled, what is the volume of the new cylinder? Thanks for your help!! Jennifer
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A cylinder has a volume of 85.6 cubic meters. If the radius is tripled and the height is doubled, what is the volume of the new cylinder?
:
The volume of a cylinder V = pi*r^2*h
You may be able to just look at this and see that it would be 18 times as much
Anyway here is method:
:
85.6 = pi*r^2*h
;
Let x = new cylinder volume
If you tripled the radius and doubled the height you could write it like this:
x = pi* (3r)^2 * 2h
x = pi * 9r^2 * 2h
:
A proportion equation:
85.6%2Fx = %28pi%2Ar%5E2%2Ah%29%2F%28pi%2A%289r%5E2%29%2A2h%29
Cancel our like terms and you have:
85.6%2Fx = 1%2F%289%2A2%29 which is: 85.6%2Fx = 1%2F18
Cross multiply:
1x = 18 * 85.6
x = 1540.8