**Practice Problem 1**

Convert 6.5 feet into inches.

**Solution**

We can start by writing an equality for the relationship between feet and inches.

12 in = 1 ft

We then divide both sides of the equality by 1 foot.

The result is a ratio, or factor, that is equal to 1. This
ratio is therefore a *unit factor.*

12 in |
= | 1 |

1 ft |

This is not the only unit factor that can be constructed. We can divide both sides of the equality by 12 inches to create another unit factor.

1 ft |
= | 1 |

12 |

in Both unit factors are valid, but only one is useful. If we choose the right unit factor, the units of feet will cancel when we multiply the original measurement by the unit factor.