# Thread: a 300 foot long cable,

1. ## a 300 foot long cable,

a 300 foot long cable, originally of diameter 5 inches, is submerged in seawater. Because of corrosion the surface area of the cable diminshes at the rate of 1250 inches^2 per year. Express dimaterew of cable d as a function of time t in years.

2. ## Re: a 300 foot long cable,

Originally Posted by sluggerbroth
a 300 foot long cable, originally of diameter 5 inches, is submerged in seawater. Because of corrosion the surface area of the cable diminshes at the rate of 1250 inches^2 per year. Express dimaterew of cable d as a function of time t in years.
Hi sluggerbroth!

Do you have a formula that relates the surface of the cable to the diameter?

3. ## Re: a 300 foot long cable,

no but i thought one might exist? can you help?

4. ## Re: a 300 foot long cable,

What do you already know and what did you try?

To be honest, I don't like to simply give the answer.
And that is also against forum policy.

5. ## Re: a 300 foot long cable,

this is a pre calc problem i found in schaums pre calculus in a chapter on inverse functions

6. ## Re: a 300 foot long cable,

Allright, so you need to set up a formula that calculates the surface as a function of the diameter.
And then you have to invert that function.

7. ## Re: a 300 foot long cable,

The circumference of a circle of radius r is $\displaystyle 2\pi r$ (I'll bet you knew that). So what is the surface area of a cylinder of radius r and length h?