7th Grade Math

Lesson 3C Composite Figures 609

B 12. SWIMMING POOLS The swimming

8 ft

14 ft

30 ft

pool at the right is being filled with 12 ft 3 ft

water. Find the number of cubic

feet that it will take to fill the

swimming pool. (Hint: The area of

a trapezoid is A = _^12 h (b 1 + b 2 ).)

13. BOXES Charlotte wants to make the box shown.

10 in.

9 in.

11 in.

What is the surface area of the box? Round to 5 in.

the nearest tenth.

14. FOOD A carryout container is shown. The

5 in.

6 in.

4 in.

4 in.

bottom base is a 4-inch square and the top base

is a 4-inch by 6-inch rectangle. The height of the

container is 5 inches. Find the volume of food

that it holds to the nearest tenth.

15 GEOMETRY Find the volume of the

5 in.

10 in.

12 in.

24 in.

figure at the right in cubic feet. Round

to the nearest tenth.

C 16. OPEN ENDED Draw a composite figure that is made up of a cylinder and

two cones. Label its dimensions and find the volume of the figure.

17. CHALLENGE Give an example of a composite figure that has a volume
    between 250 and 300 cubic units.


18. FIND THE ERROR Seth is finding the surface area of the composite figure
    shown. Find his mistake and correct it.

V = _^1

3

Bh + s 3

V = _^1

3

(^) · (^36) · 4 + 6^3
V = 264 cm^3

19. E WRITE MATH How is finding the surface area of a half-cylinder
    different from finding the surface area of a cylinder?

5 cm

6 cm

6 cm

6 cm

6 cm

4 cm

Measurement Measurement

Conversions Conversions

In Exercise 15,

remember to convert

inches to feet. 12

inches = 1 foot

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