If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Integrated math 3

### Course: Integrated math 3>Unit 9

Lesson 5: Modeling with multiple variables

# Interpreting expressions with multiple variables: Cylinder

Given the vale and the expression for the radius of a cylinder, find the radius of a cylinder with the same volume and 100 times the height. This involves analyzing the expression for the radius to see how changing the height affects the radius. Created by Sal Khan.

## Want to join the conversation?

• 1/3A-Bsquared
If I increase b the expression becomes more negative but also if I decrease b won’t the same thing happen be cause of the negative in front of the b because anything squared is positive
• A better way to word it would be "the result becomes smaller" because it won't always be negative, even when you increase b

Yes and no. If you mean that you would still subtract after decreasing b's value, then yes. If you mean that the value will be equivalent to the one before, no. This is because even though you are performing the same operations, you are working with a different value for b, making the result change. This is all assuming that A stays the same
(1 vote)
• I like to try solving these problems before I watch the video. I solved this question a little differently as a result.
I rearranged the given equation to solve for V, as both cylinders shared the same volume. I put the 20m radius on one side and the 100h on the other, then solved for r.

r = sqrt(V/h(pi)) : V = h(pi)r^2
r^2(pi)100h = h(pi)(20)^2

Thankfully I still got the same answer.