How do you solve \frac { 2} { 18} = \frac { x } { 36}?

Mar 4, 2018

Solve by doing cross multiplication, and you'll get the answer: 4

Explanation:

What is cross multiplication?

Cross Multiplication is a method of solving in which you multiply the diagonal numbers or variables, coming up with an equation that you can solve! It is also called a proportion!

Here is the procedure:

$\frac{2}{18} = \frac{x}{36}$

Let's see if we can simplify anything to make this easier...

$\frac{1}{9} = \frac{x}{36}$

After we simplified the right-hand side, we now do cross multiplication...

You then multiply $1$ and $36$ and then multiply $x$ and $9$.

That will then give you...

$9 x = 36$

that is the same as...

$36 = 9 x$

I chose the first one...

Now you solve the equation:

$9 x = 36$

Divide each side by 9 to isolate x...

$\frac{9}{9} x = \frac{36}{9}$

$1 x = 4$

$x = 4$

Now you have your answer! To check to see if it's correct, just substitute the variable with its value, simplify as much as you can, and if there is the same number on both sides at the end, the value of the variable is correct.

I hope you understood my explanation, but if you don't make sure you have a look at this Khan Academy's video on solving proportions aka cross multiplication. Or, have a look at this simple "image explanation". My source is my knowledge.