7th Grade Math

R28 Selected Answers and Solutions

Selected Answers and Solutions

3. Sample answer:

Hours Spent Exercising per Week

Hours Tally Frequency

0–2 ⁄  6

3–5 ⁄  8

6–8  3

9–11  2

12–14  1

6

8

4

0

2

10

Frequency

Hours

0–2 3–5 6–8 9–11 12–14

Hours Spent Exercising

Per Week

55 a. Look at the horizontal scale of the graph.

The countries represented in the fi rst two bars have

areas less than 401 square kilometers. Look at

the vertical scale of the graph. The fi rst bar

represents 21 countries. The second bar represents

9 countries. Add these to fi nd a total of 30 countries

with areas less than 401 square kilometers.

b. Adding the number of countries in the second

and third bars, you fi nd that 19 countries have

between 201 and 600 square kilometers. Adding

all the bars shows a total of 50 countries

represented. Find what percent 19 is of 52. Since

_^19

50 is about 0.38 or 38%, about 38% of the countries

have an area of 201–600 square kilometers.

c. Not very likely. Sample answer: Only 4 out of the

50 countries in the histogram have an area greater

than 800 square kilometers.

77 a. Seattle has a building in the 900–999 foot

range. Pittsburgh does not. Therefore, Seattle has the

tallest building. b. Pittsburgh has a building in that

range, while Seattle does not. c. Pittsburgh has

3 + 1 + 1 or 5 buildings in that range. Seattle has

3 + 3 + 1 or 7 buildings in this range. Therefore,

Seattle has more buildings in the range. Adding all of

the buildings represented by the bars, Seattle has a

total of 21 buildings. Since _ 217 is about 0.33 or 33%,

about 33% of the buildings are 600 feet or taller.

d. Seattle has 6 more buildings than Pittsburgh.

11. Sample answer: A histogram is like a bar graph
    because it displays data. A histogram is different
    because it uses intervals of numbers instead of one
    specifi c category. 13. ^45 15. ^23

Pages 528–530 Lesson 9-3E

1. Height of Trees (ft)
   Stem Leaf
   0
   1
   2

8 8

0 2 5 5 6 8

0 5 (^2) | 0 = 20 ft
33 a. range: oldest - youngest =^14 - 9 or 5 years
b. median: middle value, or 11 years; mode: most
frequent value, 11 years c. The mean would be
most affected because it would decrease.

5. Low Temperatures (°F)
   Stem Leaf
   1
   2
   3

3 3 5

0 4 8

0 1 2 2 5 6 8 8 8 (^1) | 3 = 13°F

7. School Play
   Attendance
   Stem Leaf
   22
   23
   24
   25
   26
   27

5 7 9

0

3 6

7 9 9

8 8 8 (^26) | 7 = 267
9a. $45 9b. $108 and $115 9c. mean
1111 There are no numbers that are outliers. As the
score goes up, fewer people can achieve it.
Gymnastics Scores
Stem Leaf
8
9
10
9 5 7 7 8
0 3 3 9
(^0 8) | 9 = 8.9
Sample answer: There is only one person who
scored a perfect 10. An average score is about 9.1.

15. Sample answer: Aisha read the plot incorrectly.
    There are two pieces of ribbon that are more than
    50 inches at 53 and 56 inches. 17. C 19. median
    or mode; Sample answer: Class B has a median of


16. Class A has a median of 79. 80 > 79; Class B has
    a mode of 79. Class A has a mode of 72. 79 > 72


17. no; Sample answer: Class A’s mean score is 80%
    and Class B’s mean score is 79%. Since 80% and
    79% are close, each class has about the same
    average. 23. 20 g; 36 g 25. chicken; Sample
    answer: Chicken sandwiches have 8–20 grams of
    fat. Burgers have 10–36 grams of fat.

Pages 532–533 Lesson 9-4A PSI

1. about 6 _^12 tablespoons 3. about $33.83
   55 If two workers make 2 chairs in 2 days, it
   takes each worker 2 days to make 1 chair. In
   20 days, a worker could make 10 chairs. Eight
   workers could therefore make 80 chairs in 20 days.

R01_R42_EM_SelAns_895130.indd R28 1/18/10 9:51 AM