solving proportions 4-2 bell work: find two ratios that are equivalent to each given ratio. 3535 1....
TRANSCRIPT
Solving Proportions4-2
Bell work:Find two ratios that are equivalent to each given ratio.
35
1.
4530
3. 9060
32
,
1012
2. 2024
56
,
89
4. 2427
1618
,
915
610
,Possible answers:
Solving Proportions4-2
Problem of the DayWhat is the better buy?
A $1.29 pack of gum that has 15 pieces,OrA $1.59 pack of gum that has 20 pieces?
Explain your answer.
Solving Proportions4-2
Learning Target: I can tell if ratios are proportional.I can solve a proportion.
Solving Proportions4-2
Vocabulary
RatioRatio
ProportionProportion
Cross ProductCross Product
Solving Proportions4-2
Tell whether the ratios are proportional.
410
615
Since the cross products are equal, the ratios are proportional.
60
=?
60 = 60
Find cross products.60410
615
Solving Proportions4-2
Tell whether the ratios are proportional.
Since the cross products are equal, the ratios are proportional.
20
20 = 20
Find cross products.2024
510
24
510
=?
Solving Proportions4-2
A mixture of fuel for a certain small engine should be 4 parts gasoline to 1 part oil. If you combine 5 quarts of oil with 15 quarts of gasoline, will the mixture be correct?
4 parts gas1 part oil
=? 15 quarts gas5 quarts oil
4 • 5 = 20 1 • 15 = 15
20 ≠ 15
The cross products are not equal. The mixture will not be correct.
Set up equal ratios.
Find the cross products.
Solving Proportions4-2
A mixture for a certain brand of tea should be 3 parts tea to 1 part sugar. If you combine 4 tablespoons of sugar with 12 tablespoons of tea, will the mixture be correct?
3 parts tea 1 part sugar
=? 12 T tea4 T sugar
3 • 4 = 12 1 • 12 = 12
12 = 12
The cross products are equal. The mixture will be correct.
Set up equal ratios.
Find the cross products.
Solving Proportions4-2
The ratio of boys to girls in a soccer league is 5:4. If there are 55 boys in the league, how many girls are there?
54
boysgirls
=
54
=55x
x = 44
5x = 220
There are 44 girls in the league.
Solving Proportions4-2
The ratio of cats to dogs at a kennel is 3:2. If there are 48 dogs at the kennel, how many cats are there?
32
CatsDogs
=
32
= x48
x = 72
2x = 144
There are 72 cats at the kennel.
Solving Proportions4-2
A banana slug travels 4.5 inches in 120 minutes. At this rate of speed, how long would it take the slug to travel 12 inches?
4.5 in120 min
= 12 ins
One option is to use a proportion: inches/minute.
4.5s = 1440
s = 320 minutes
Solving Proportions4-2
A cable car travels 15 miles in 80 minutes. At this rate of speed, how long would it take the cable car to travel 45 miles?
x = 240
15 miles80 min
= 45 milesx
15x = 3600
Solving Proportions4-2
Lesson Quiz
Tell whether the ratios are proportional.
4842 =? 16
141. 40
15 =? 34
2.
Solve each proportion.
3. 4.
5. An elevator travels 342 feet as it goes from the lobby of a building to the top floor. It takes 7 seconds to travel the first 133 feet. If the elevator travels at the same rate, how much longer does it take reach the top floor?
yes no
n = 30 n = 16
11s
4518
n12 = n
2469 =
Solving Proportions4-2
Assignment:
Lesson 4.2, page 164, 9-16, 26-31