How to do proportions?
Solving proportions is simply a matter of stating the ratios as fractions, setting the two fractions equal to each other, cross-multiplying, and solving the resulting equation. You'll probably start out by just solving proportions, like this: Find the unknown value in the proportion: 2 : x = 3 : 9.
A proportion is just two fractions set equal to each other
So, when solve a proportion, you cross multiply
\(\frac{x}{3}\) = \(\frac{3}{4}\)
So, multilpy the top of the fraction on the left by the bottom of the fraction on the right
x · 4 = 4x
Now, multiply the bottom of the left by the top of the right
3 · 3 = 9
Now, set these two products equal to each other
4x = 9
Divide by 4 to isolate x
x = \(\frac{9}{4}\)