1. Proportions

2. A proportion is simply a statement that two ratios are equal
A proportion is simply a statement that two ratios are equal. It can be written in two ways: as two equal fractions a/b = c/d; or using a colon, a:b = c:d.

3. We can also cross multiply to find a missing term in a proportion
We can also cross multiply to find a missing term in a proportion. Here's an example:

4. In a horror movie featuring a giant beetle, the beetle appeared to be 50 feet long. However, a model was used for the beetle that was really only 20 inches long. A 30-inch tall model building was also used in the movie. How tall did the building seem in the movie?

5. First, write the proportion, using a letter or symbol to stand for the missing term.
50 = ?

6. Next, simply cross multiply the two numbers we know.
50 = ?
50 x 30= 1,500

7. Next, we divide by the number we didn’t use to find out our missing number.
50 = ?
20)1500

8. Finally, we solve! 75
20) 1500

9. Example: = 4 t
Find t:

10. Example: = ?
Find ?: