Ratios, Rates, and Unit Rates

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7-2
Ratios, Rates, and Unit Rates
Lesson Presentation
Pre-Algebra
2
A. Order the ratios 43, 2310, 139, and 4720
from the least to greatest.
43
2.3
2310
2.35
139
4720
The ratios in order from least to greatest are
43, 139, 2310, and 4720.
3
B. A television has screen width 20 in. and
height 15 in. What is the aspect ratio of this
screen?
The ratio of the width to the height is 2015.
The screen has the aspect ratio 43.
4
A ratio is a comparison of two quantities.
A rate is a comparison of two quantities that
have different units.
Read as 90 miles per 3 hours.
90 3
90 miles 3 hours
Ratio
Rate
Unit rates are rates in which the second quantity
is 1.
30 miles, 1 hour
Unit rate
or 30 mi/h
5
Additional Example 2 Using a Bar Graph to
Determine Rates
Use the bar graph to find the number of acres, to
the nearest acre, destroyed in Nevada and Alaska
per week.
640,000 acres 52 weeks
Nevada
12,308 acres 1 week
?
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Additional Example 2 Continued
Use the bar graph to find the number of acres, to
the nearest acre, destroyed in Nevada and Alaska
per week.
750,000 acres 52 weeks
Alaska
14,423 acres 1 week
?
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Try This Example 2
Use the bar graph to find the number of acres, to
the nearest acre, destroyed in Montana and Idaho
per week.
950,000 acres 52 weeks
Montana
18,269 acres 1 week
?
8
Try This Example 2 Continued
Use the bar graph to find the number of acres, to
the nearest acre, destroyed in Montana and Idaho
per week.
1,400,000 acres 52 weeks
Idaho
26,923 acres 1 week
?
9
Unit price is a unit rate used to compare costs
per item.
Pens can be purchased in a 5-pack for 1.95 or a
15-pack for 6.20. Which is the better buy?
price for package number of pens
1.95 5
0.39

?
6.20 15
price for package number of pens
0.41
?

The better buy is the 5-pack for 1.95.
10
Golf balls can be purchased in a 3-pack for 4.95
or a 12-pack for 18.95. Which is the better buy?
price for package number of balls
4.95 3

1.65
?
price for package number of balls
18.95 12
?
1.58

The better buy is the 12-pack for 18.95.
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Lesson Quiz
1. At a family golf outing, a father drove the
ball 285 ft. His daughter drove the ball 95 ft.
Express the ratio of the fathers distance to his
daughters in simplest terms. 2. Find the unit
price of 6 stamps for 2.22. 3. Find the unit
rate of 8 heartbeats in 6 seconds. 4. What is the
better buy, a half dozen carnations for 4.75 or
a dozen for 9.24? 5. Which is the better buy,
four pens for 5.16 or a ten-pack for 12.90?
31
0.37 per stamp
? 1.3 beats/s
a dozen
They cost the same.
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Homework

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