1. Learn to solve proportions by cross multiplying.

2. Insert Lesson Title Here
Example 1
Use cross products to solve the proportion. 6 7 = m 14
7 · m = 6 · 14
The cross products are equal.
7m = 84
Multiply. 7m 7 84 7 =
Divide each side by 7 to isolate the variable.
m = 12

3. In proportions that include different units of measurement, either
the units in the numerators must be the same and the units in the denominators must be the same or
the units within each ratio must be the same.
16 mi
4 hr
8 mi
x hr
16 mi
8 mi
4 hr
x hr = =

4. If 3 of Jennifer’s books takes up 4 inches of space on her shelf, how much space will she need for all 26 volumes?

5. Additional Example 2 Continued
Set up a proportion using the given information. Let x represent the inches of space needed.
3 volumes
4 inches
26 volumes x
volumes
inches =

6. Additional Example 2 Continued
Solve 3 3 4 26 x
Write the proportion. =
3 · x = 4 · 26
The cross products are equal.
3x = 104
Multiply. 3x 3
104 3
Divide each side by 3 to isolate the variable. = 2 3
x = 34 2 3
She needs 34
inches for all 26 volumes.

7. Example 3
John filled his new radiator with 6 pints of coolant, which is the 10 inch mark. How many pints of coolant would be needed to fill the radiator to the 25 inch level?

8. Check It Out: Example 2 Continued
Make a Plan
Set up a proportion using the given information. Let p represent the pints of coolant.
6 pints
10 inches p
25 inches
pints inches =

9. Check It Out: Example 2 Continued
Solve 3 6 10 p 25
Write the proportion. =
10 · x = 6 · 25
The cross products are equal.
10x = 150
Multiply.
10x 10
150 10
Divide each side by 10 to isolate the variable. =
p = 15
15 pints of coolant will fill the radiator to the 25 inch level.

10. Check It Out: Example 2 Continued4
Look Back
10 · 15 = 150 6 10 15 = 25
6 · 25 = 150
The cross products are equal, so 15 is the answer.

11. Insert Lesson Title Here
Solve on the sheet of paper. Show all steps.
11/14/16
Carmen bought 3 pounds of bananas for $1.08. June paid $ 1.80 for her purchase of bananas. If they paid the same price per pound, how many pounds did June buy?
5 pounds

12. Ingrid types 3 pages in the same amount of time that Tanya types 4
Ingrid types 3 pages in the same amount of time that Tanya types 4.5 pages. If Ingrid and Tanya start typing at the same time, how many pages will Tanya have typed when Ingrid has typed 11 pages?

13. The waiting time to ride a roller coaster is 20 minutes when 150 people are in line. How long is the waiting time when 240 people are in line?

14. A 6-ounce package of fruit snacks contains 45 pieces
A 6-ounce package of fruit snacks contains 45 pieces. How many pieces would you expect in a 10-ounce package?