Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Sodium chlorate crystals are easy to grow in the shape of cubes by allowing a solution of water and sodium chlorate to evaporate slowly. If $V$ is the volume of such a cube with side length $x$, calculate the derivative when $x = 4 \text{ mm}$.

$$V'(4) = \cdots \text{ mm}^3/\text{mm}$$

I thought that:

$$V'(4) = 64 \text{ mm}^3/\text{mm}$$

Because volume of a cube $=$ $4 \times 4 \times 4$

share|cite|improve this question
In your first equation, what is the "?" supposed to represent? I think if you replace that with the correct derivative of V(x), you'll be able to find your answer. Just to be clear: write the equation for the volume of a cube with side length x, then take the derivative of that equation, then plug in 4. – Todd Wilcox Oct 22 '12 at 4:19
an unknown number – dsta Oct 22 '12 at 4:20
I don't have an equation. – dsta Oct 22 '12 at 4:21
Try searching the internet or your calculus book for equation for the volume of a cube. – Todd Wilcox Oct 22 '12 at 4:21
So the answer would be 48. Thank you!!! – dsta Oct 22 '12 at 4:23

$V(x)=x^3$ is the volume of a cube with side $x$. Take the derivative of that to get $V'(x)$ and then calculate $V'(4)$.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.