Ratios and percentages are different ways of expressing a part of a whole number. A percentage is a means of expressing a fraction of one hundred. For example, 25 percent means 25 out of 100. A ratio is a means to express a percentage in the simplest possible way. For example, 25 percent can be reduced to a ratio of 1:4. Simple rules can be used to turn a percentage into a ratio.

Write down the percentage that needs to be converted. For example, suppose you want to convert 35 percent.

Express the percentage as a simple fraction of 100. In the example, you would have determine that 35 percent equals 35 / 100.

Determine the highest possible whole number that can be used to divide the upper (numerator) and lower (denominator) part of the fraction that results in another whole number. This is known as the greatest common factor. In the example, both 35 and 100 are divisible by 5, and this operation leads to two whole numbers:

35 divided by 5 = 7

100 divided by 5 = 20

Therefore, the simplified fraction is 7 / 20.

Write the simplified fraction as a ratio by using the colon symbol. In the example, you would write 7 / 20 as "7:20."