75

3020

8

2

3

18

27

5.4

5.2

13

5.7

36

5.22

24

15A) and B) and C) and D. and

Determine which pair of ratios does NOT form a proportion.

Method 1: Check the cross products. Crossproducts of proportions arealways equal.

For example:30(20)=600 and 8(75)=600So

does form a proportion.

75

3020

8

Method 2: Convert eachratio to a decimal. Both ratioswill equal the same decimalvalue if they form a proportion.

For example:30/75= .4 and 8/20 = .4So

does form a proportion.

75

3020

8

Do the following pairs of ratios form proportions?

5.4

12

3

8

20

6

27

9

12(3)=36 and 8(4.5)=36So they do form a proportion

9(20)=180 and 6(27)=162So they do not form a proportion

Use a proportion to determine whether or not the two candy bars below contain an equal proportion of sugar.

Snickers: A 59 gram candy bar contains 30 grams of sugar. Milky Way: A 72 gram candy bar contains 35 grams of sugar.

sugarg

barg

sugarg

barg

35

72?

30

59

21602065

)30(72?)35(59

Since the cross products are not equal the bars do notContain an equal proportion of sugar!

Use a proportion to determine whether or not the two bagsof potato chips below contain an equal proportion of carbs.

Lays: A 40 gram bag contains 14 grams of carbs. Ruffles: A 60 gram bag contains 21 grams of carbs.

carbsg

bagg

carbsg

bagg

21

60?

14

40

840840

)14(60?)21(40

Since the cross products are equal the bagscontain an equal proportion of carbs!

A 12 ounce can of Coke costs $0.75 when purchased from the soda machine at the school. An 18 ounce bottle of Pepsi from the soda

machine at the local gas station costs $1.25. Find the unit cost of each to determine which location has the less expensive soda per ounce?

ounceper

ounceper

07$.18/25.1

06$.12/75.

Coke

Pepsi

Coke is the better deal because it is $.01 cheaper per ounce

A 20 ounce bag of potato chips costs $3.99 at the store. The same brand of chips costs $.50 for 3 oz

in the vending machine.

Find the unit price for each ounce and determinethe better deal.

ounceper

ounceper

17$.3/50.

20$.20/99.3

Store

Vend

The vending machine has the better dealbecause those chips cost 3 cents moreper ounce.

The ratio of teachers to students in the gym is 2 to 9. How many teachers are in the gym if there is a total of 165 students and teachers

altogether in the gym?

teachers

total

teachersx

total

teachers

302)165(11

16511

2

The problem tells you that in the ratio there are 2 teachersTo every 9 students. Next, it gives you the total number of 165. This means you need the total in the ratio of 9+2=11

The ratio of fish to snails in an aquarium is 4 to 5. How many fish are in the aquarium if there is a total of 117 fish and snails

altogether in the aquarium?

fish

total

fishx

total

fish

529)117(4

1179

4

40

30

7

4

15

12

20

15

12

4

Which ratio is equivalent to ?

You can simplify each ratio or changeeach ratio to a decimal to compare.

Both and simplify to or .75 so they are equivalent40

3020

15

4

3

4518

6

4

2

1

10

4

91

Which ratio is equivalent to ?

You can simplify each ratio or changeeach ratio to a decimal to compare.

Both and simplify to or .4 so they are equivalent

4518

104

5

2