Geometry Area, Volume and Dissection Arguments Worksheet Solutions (PDF)

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This geometry area volume answers for Geometry covers area, volume and dissection arguments (Common Core G-GMD.A.1, G-GMD.A.3), with a free PDF to print.

Use this answer key to check the 20 problems on volume formulas. Every solution shows the formula or theorem used, each step of the work, and the final answer in bold. If an answer differs from yours, compare the steps line by line to find where the work changed.

Geometry · Common Core State Standards: G-GMD.A.1, G-GMD.A.3

Geometry area volume answers: exercises 1 to 10

Exercise 1 – Circumference and area

\(C = 2\pi \cdot 7 = 14\pi\).

\(A = \pi \cdot 7^{2} = 49\pi\).

14π and 49π

Exercise 2 – Area from the diameter

Radius 5.

\(A = 25\pi = 78.5\)

78.5 square units

Exercise 3 – Cylinder volume

310
V = 90π.

\(V = \pi \cdot 3^{2} \cdot 10 = 90\pi\) = 282.7.

90π, about 282.7 cubic units

Exercise 4 – Cylinder from the diameter

Radius 4.

\(V = \pi \cdot 4^{2} \cdot 12 = 192\pi = 603.2\)

603.2 cubic inches

Exercise 5 – Cone volume

96
V = 108π.

\(V = \frac{1}{3}\pi \cdot 6^{2} \cdot 9 = 108\pi = 339.3\)

108π, about 339.3

Exercise 6 – Cone with slant height

Height: \(\sqrt{13^{2} – 5^{2}} = 12\).

\(V = \frac{1}{3}\pi \cdot 25 \cdot 12 = 100\pi = 314.2\)

Height 12; V = 100π, about 314.2

Exercise 7 – Sphere volume

3
V = 36π.

\(V = \frac{4}{3}\pi \cdot 3^{3} = 36\pi = 113.1\)

36π, about 113.1

Exercise 8 – Larger sphere

\(V = \frac{4}{3}\pi \cdot 6^{3} = 288\pi = 904.8\)

904.8 cubic units

Exercise 9 – Square pyramid

Base area \(8^{2} = 64\).

\(V = \frac{1}{3} \cdot 64 \cdot 9 = 192\)

192 cubic units

Exercise 10 – Rectangular pyramid

\(V = \frac{1}{3} \cdot (6 \cdot 10) \cdot 7 = 140\)

140 cubic units

Exercises 11 and up

Exercise 11 – Hemisphere

Half of a sphere: \(\frac{1}{2} \cdot \frac{4}{3}\pi \cdot 6^{3} = 144\pi = 452.4\)

452.4 cubic units

Exercise 12 – Find the radius

\(\pi r^{2} \cdot 8 = 200\pi\)

\(r^{2} = 25\), so \(r = 5\).

r = 5

Exercise 13 – Cavalieri

straight stackslanted stacksame height
Cavalieri’s principle: equal heights and equal cross-sections give equal volumes.

Right prism: \(40 \cdot 9 = 360\).

By Cavalieri’s principle, the slanted prism has the same volume, 360.

360 for both

Exercise 14 – Cone and cylinder

The cone has one third of the volume.

\(\frac{1}{3} \cdot 150\pi = 50\pi\)

50π

Exercise 15 – Pyramid in a cube

Cube: \(6^{3} = 216\). Pyramid: \(\frac{1}{3} \cdot 36 \cdot 6 = 72\).

\(216 \div 72 = 3\) pyramids fill the cube.

216; 72; 3 pyramids

Exercise 16 – Doubling the radius

\(\frac{4}{3}\pi(2r)^{3} = 8 \cdot \frac{4}{3}\pi r^{3}\), so the volume is 8 times as large.

Check: \(\frac{32}{3}\pi\) and \(\frac{256}{3}\pi\), a ratio of 8.

Factor of 8

Exercise 17 – Water tank

\(V = \pi \cdot 4^{2} \cdot 10 = 160\pi = 502.7\) cubic feet.

\(502.7 \cdot 7.48 = 3,760\) gallons.

502.7 cu ft; about 3,760 gallons

Exercise 18 – Ice cream cone

Cone: \(\frac{1}{3}\pi \cdot 3^{2} \cdot 10 = 30\pi\).

Hemisphere: \(\frac{2}{3}\pi \cdot 3^{3} = 18\pi\).

\(30\pi + 18\pi = 48\pi = 150.8\)

150.8 cubic centimeters

Exercise 19 – Grain silo

Cylinder: \(\pi \cdot 10^{2} \cdot 30 = 3000\pi\).

Hemisphere: \(\frac{2}{3}\pi \cdot 10^{3} = \frac{2000}{3}\pi\).

\(3000\pi + \frac{2000}{3}\pi = \frac{11000}{3}\pi = 11,519\)

About 11,519 cubic feet

Exercise 20 – Sand pile

Radius 6.

\(V = \frac{1}{3}\pi \cdot 6^{2} \cdot 5 = 60\pi = 188.5\)

188.5 cubic feet

Key facts behind this geometry area volume answers

Key facts
  • Circle: C = 2 pi r, A = pi r squared.
  • Prism and cylinder: V = Bh.
  • Pyramid and cone: V = (1/3)Bh.
  • Sphere: V = (4/3) pi r cubed.
  • Cavalieri’s principle: same height and same cross-sectional areas give the same volume.

How to use this geometry area volume answers

Cover each solution, solve the exercise again, then uncover it and compare every line. If your answer differs, find the first step that changed and redo the exercise from there.

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Geometry Area, Volume and Dissection Arguments Worksheet Solutions

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