7th Grade Math

Chapter Study Guide and Review 615

Composite Figures

PSI: Solve a Simpler Problem (Lesson 3A)

31. LAND A rectangular plot of land measures
    1,450 feet by 850 feet. A contractor wishes
    to section off a portion of this land to
    build an apartment complex. If the
    complex is 425 feet by 550 feet, how
    many square feet of land will not be
    sectioned off to build it?


32. TRAVEL Mrs. Whitmore left Chicago at
    6:45 a.m. and arrived in St. Louis at
    11:15 a.m., driving a distance of
    approximately 292 miles. Find her
    approximate average speed.


33. SHOPPING Mercedes spent $175.89 over
    the weekend. Of the money she spent,
    40% was spent on shoes. About how much
    money was not spent on shoes?

EXAMPLE 8 A total of 950 residents voted

on whether to build a neighborhood

playground. Of those that voted, 70% voted

for the playground. How many residents

voted for the playground?

Find 10% of 950 and then use the result to

find 70% of 950.

10% of 950 = 95

Since there are seven 10s in 70%, multiply

95 by 7.

So, 95 × 7 or 665 residents voted for the

playground.

Volume and Surface Area of Composite Figures (Lesson 3C)

Find the volume of each composite figure.

Round to the nearest tenth if necessary.

34. 4 ft

5 ft

5 ft

12 ft

6 ft

35.

2 m

3 m

2.5 m

4 m

36. MAILBOX Berdina

3 ft

3 ft

4 ft

1.5 ft

is helping her dad

paint a mailbox like

the one shown. If

one quart of paint

covers 40 square

feet, how many

quarts of paint

should they buy?

EXAMPLE 9 Joey built a small greenhouse

shown below. What is the volume of the

greenhouse?

Volume of 1 yd

1.2 yd

1.5 yd

0.8 yd

rectangular prism

= wh

= (1.5)(0.8)(1.2)

= 1.44 yd^3

Volume of pyramid

= _ 31 Bh

= _^13 (1.2)(1)

= 0.4 yd^3

1.44 + 0.4 = 1.84 cubic yards

So, there are 1.84 cubic yards in the

greenhouse.

Lesson 3

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