The Crayola crayon company can make 2400 crayons in 4 minutes. How many crayons can they make in 15 minutes?

To solve this problem we begin by making a table and filling in the given information.

We put "x" under crayons because we don't know how many crayons are made in 15 minutes.

Now solve the proportion:

$\frac{2400}{x}=\frac{4}{15}$

$x=9000\mbox{ crayons}$

A typist can type 120 words in 100 seconds. At that rate, how many seconds would it take her to type 258 words?

To solve this problem we begin by making a table and filling in the given information.

We put "x" under seconds because we don't know how many seconds it takes to type 258 words.

Now solve the proportion:

$\frac{120}{258}=\frac{100}{x}$

$x=215\mbox{ seconds}$

Example 1

A can of tomato paste weighs 16 ounces and/or 452 grams. This depends on whether you use English measurement or SI.
Make a ratio table to determine the number of ounces in a kilogram (1000 grams).

 $\frac{16}{x}=\frac{452}{1000}$

$16\cdot~1000\,=\,452\cdot~x$

$16000\,=\,452\cdot~x$

$35.398\,=\,x$

This means there are about 35.4 ounces in 1 kilogram. 

Example 2

Measuring miles on the ocean (nautical miles) is different from "normal" miles on land (statute miles). In fact, 100 nautical miles is equal to 115 statute miles.

If you plan on going 92 statute miles, how many nautical miles would you have to travel?

$\frac{100}{x}=\frac{115}{92}$

$100\cdot~92\,=\,115\cdot~x$

$9200\,=\,115\cdot~x$

$80\,=\,x$

This means there are 80 nautical miles for every 92 statute miles.