Using Conversion Factors

Problem: A football field is 100 yards long. How many inches is that?


We know the common conversions from yards to feet and feet to inches are 3 feet = 1 yard and 12 inches = 1 foot.

The conversion fact 3 feet = 1 yard has two conversion factors: conversion factors

The conversion fact 12 inches = 1 foot also have two conversion factors: conversion factors

Now we must select the proper conversion factors in fraction form that will convert yards to inches. Using the following template, we start with yards, then yards and feet will cancel out leaving inches and the first fraction is the conversion factor for yards to feet, and the second fraction will be the conversion factor for feet to inches:

Now filling in the problem number of 100 and the conversion factor numbers we have:

Now we use our calculator to determine how many inches are equivalent to 100 yards by entering the numbers from the above expression. Use the following keypresses:


TI84 screen

We find that 100 yards is equivalent to 3600 inches.


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