Proportion
Object
Centimeters
Inches
 cm 


 in 
Unit Rate
1. Measure the length or width of each of six different-sized objects, such as a pencil, a book, your desk, or
your calculator, etc. For each object, record the inch measurement and the centimeter measurement in
the table.
2. Compare the two types of measurements for each by putting the centimeters over the inches in a fraction
(a ratio). Record the ratio in your table as a unit rate.
3. How do the unit rates of centimeters to inches compare for the different measurements? (If one of the
unit rates is much different from the others, recheck your measurements.)
4. Pick one ratio of centimeters to inches from your table. Write a sentence that explains the meaning of
this ratio.
5. The common ratio you found for centimeters to inches (the unit rate) is called a conversion factor. Use
the conversion factor, set a proportion, and convert each length.
6. Using your ratio, set up a proportion and convert each length:
a. 215 cm = x in
b. 5 cm = x in
c. 15 in = x cm
7. Jonas drove his car from Montana to Canada on vacation. While there, he needed to buy gasoline and
noticed that it was sold by the liter rather than by the gallon. Use the conversion factor 1 gal  3.79 L to
determine how many liters will fill his 12.5-gallon gas tank.