The formula c = 2.54i relates inches and centimeters, where c is the length in centimeters and i is the length in inches. A pencil is 5 inches long. What is its length in centimeters?

The formula c = 2.54i is interpreted as "the number of centimeters is 2.54 groups of the number of inches".

This means if you know the number of inches you will multiply it by 2.54 to convert it to centimeters.

In this example, you will multiply 2.54 x 5 to get 12.7 centimeters,

5 inches = 12.7 centimeters