Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

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

I guess this should be very easy, but I'm stuck.

I have a rectangle:

Area = $520\text{ cm}^2$

$x = 120\text{ cm}$

$y = ?$


Area = $x \cdot y$

$520 \text{ cm}^2 = 120\text{ cm} \cdot y$

And honestly I don't know what to do. If I sqrt everything, result is wrong.

share|cite|improve this question
The thing is "division". Ask yourself, what, when multiplied by 120, gives 520? – Shubham May 24 '14 at 8:51
up vote 4 down vote accepted

You have the equation, $520 \text{ cm}^2 = 120 \text{ cm} \cdot y$. Now divide both sides by $120 \text{ cm}$.

share|cite|improve this answer

Step 1: Recall $ Area = x . y $

Step 2: Make $y$ the subject of the equation, i.e, divide both side by $x$ $\Rightarrow \frac{Area}{x} = \frac{x.y}{x} $ $\Rightarrow \frac{Area}{x} = y$

So now the formula you need to apply is $ y = \frac{Area}{x}$

I guess you became confused with the unit $ cm^2$ this is natural, what you need to realize is that the unit of $Area$ is $ cm^2$, unit of $x$ is $ cm$ and that oof $y$ is $ cm$ . so using the formula $ Area = x . y $ we have $ cm^2 = cm. cm$ now when you apply $ y = \frac{Area}{x}$ this affects the unit as follows $ cm = \frac {cm^2}{cm}$ which can be simplified to $\Rightarrow cm = \frac {cm . cm}{cm}$ now by cancelling you get $\Rightarrow cm = cm$ , you don't have to do square root in any of the steps.

If you are confused with units of problems like this, plug the units in the formula you are using and simplify, if your method is correct, unit at right side should be equal to the unit on the left side.

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.