Download Ratios, Rates, and Proportions Reteaching printing key

Determine which pair of ratios does NOT form a proportion.
A)
30
75
and
8
20
B)
3
2
and
27
18
C)
2.5 and 7.5
4 .5
13
D.
22.5
36
and
15
24
Method 1: Check the
cross products. Cross
products of proportions are
always equal.
Method 2: Convert each
ratio to a decimal. Both ratios
will equal the same decimal
value if they form a proportion.
For example:
30(20)=600 and 8(75)=600
So 30
8
For example:
30/75= .4 and 8/20 = .4
So 30
8
75
20
does form a proportion.
75
20
does form a proportion.
Do the following pairs of
ratios form proportions?
8
3
12
4.5
12(3)=36 and 8(4.5)=36
So they do form a proportion
9
27
6
20
9(20)=180 and 6(27)=162
So 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.
59 g bar
72 g bar
?
30 g sugar 35 g sugar
59(35) ? 72(30)
2065  2160
Since the cross products are not equal the bars do not
Contain an equal proportion of sugar!
Use a proportion to determine whether or not the two bags
of 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.
40 g bag 60 g bag
?
14 g carbs 21g carbs
40(21) ? 60(14)
840  840
Since the cross products are equal the bags
contain 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?
Coke .75 / 12  $.06 per ounce
Pepsi 1.25 / 18  $.07 per ounce
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 determine
the better deal.
Store 3.99 / 20  $.20 per ounce
Vend .50 / 3  $.17 per ounce
The vending machine has the better deal
because those chips cost 3 cents more
per 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?
The problem tells you that in the ratio there are 2 teachers
To 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
2 teachers x teachers

11total
165 total
11(165)  2  30 teachers
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?
4 fish
x fish

9 total 117 total
4(117)  9  52 fish
Which ratio is equivalent to
30
40
12
15
15
20
4
7
?
4
12
You can simplify each ratio or change
each ratio to a decimal to compare.
Both
30
40
and
15
20
simplify to
3
4
or .75 so they are equivalent
Which ratio is equivalent to
18
45
1
2
4
10
4
6
?
1
9
You can simplify each ratio or change
each ratio to a decimal to compare.
Both
18
45
and
4
10
simplify to
2
5
or .4 so they are equivalent