# Word problem-I would like to check my procedure

1. Oct 15, 2009

### stanton

1. The problem statement, all variables and given/known data

A cubical ice block is melting at a rate that relates to its surface area. Set up an equation for the volume of a cube, C, in terms of its surface area, S.

2. Relevant equations

C=x^3
S=6x^2

3. The attempt at a solution

let length of the side of the cube:x
dC/dx=3x^2 dS/dx=12x dC/dS=x/4
Now what should I do? I think I did pretty well untill now. How should I use this information for getting the answer? Or dC/dS(which is x/4) is the final answer?

Last edited: Oct 15, 2009
2. Oct 15, 2009

### symbolipoint

You are almost half-way there, and this is not a calculus problem.

Work with S and find a formula for x.

3. Oct 15, 2009

### stanton

Thank you. But work with S? Would you mind if I want more specific explanation from you? Sorry, cause I am not very good at math, interpreting word problems.

4. Oct 15, 2009

### HallsofIvy

Staff Emeritus
The problem said "Set up an equation for the volume of a cube, C, in terms of its surface area, S". That's why you need to "work with S".
You have $C= x^3$. You also know that [/itex]S= 6x^2[/itex].

Solve $S= 6x^2$ for x (which is a length and so positive) and replace the "x" in $C= x^3$ with that/