# I'm stuck and can't get out.

1. Nov 28, 2003

### Superman89

I'm stuck can anybody help me? (Note: I'm looking for the length.)

1,800cc-72cm=L

What do I do next?

2. Nov 28, 2003

### chroot

Staff Emeritus
Well, what you've posted does not make sense. You cannot subtract a length (cm) from a volume (cc). Perhaps you can show us the WHOLE problem?

- Warren

3. Nov 28, 2003

### Superman89

Well maybe I haven't got it written out right. Can I give you the problem and you work it out and show me how to do it?

4. Nov 28, 2003

### chroot

Staff Emeritus
Like I just said, yes, please post the entire problem.

- Warren

5. Nov 28, 2003

### Superman89

Here it is.

How long must a rectangular box be in oder to hold 1,800 cubic centimeters if its width is 12 centimeters and its height is 6 centimeters?

6. Nov 28, 2003

### chroot

Staff Emeritus
Okay, you've already posted this once. Why did you start a new thread on it?

Here's how to solve it:

$$\begin{equation*} \begin{split} V &= w \cdot l \cdot h\\\\ l &= \frac{V}{w \cdot h}\\\\ l &= \frac{1,800}{12 \cdot 6} \end{split} \end{equation*}$$

Does this make sense?

- Warren

7. Nov 28, 2003

### Superman89

Let me see if I've got this straight.

When "w" and "h" are brought arcross the "=" sign, the oppisite must be done.

$V=l*w*h$

$\frac {V}{w*h}=l$

Right?

8. Nov 28, 2003

### chroot

Staff Emeritus
It's easier to think about it this way: performing the same operation to both sides of an equation does not change the equation's validity.

In other words, if you have an equation like $a=b$, adding one to both sides of it does not change its truth: $a+1=b+1$ is also true.

In the case of the equation $V = l \cdot w \cdot h$, you can divide both sides by $w \cdot h$ and not change the equation's valitiy.

$$\begin{equation*} \begin{split} \frac{V}{w \cdot h} &= \frac{l \cdot w \cdot h}{w \cdot h}\\\\ \frac{V}{w \cdot h} &= l \end{split} \end{equation*}$$

- Warren

9. Nov 28, 2003

### Superman89

I see what you mean. So my answer is going to be $$l &= \frac{1,800}{12 \cdot 6}\end{split}\end{equation*}$$?

10. Nov 28, 2003

### chroot

Staff Emeritus
Didn't I already say that?

- Warren

11. Nov 28, 2003

### Superman89

Thanks! You've been a real good help Dude!

12. Nov 28, 2003

### chroot

Staff Emeritus
Anytime.

- Warren

13. Nov 30, 2003

### uart

Well fisrt thing I'd do is to get that X-Ray vision tested there Superman. ;)

Looks to me like when you copied the "answer" of L = 1800cc - 72 cm from whoever that you misread a divide symbol for a minus symbol.

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