Solving Problems with Volume Formulas

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Geometry › Solving Problems with Volume Formulas

Questions 1 - 10
1

A cylindrical can has diameter $10\text{ cm}$ and height $12\text{ cm}$. What is the volume of the can in cubic centimeters?

$300\pi\text{ cm}^3$

$240\pi\text{ cm}^3$

$600\pi\text{ cm}^3$

$120\pi\text{ cm}^3$

Explanation

This problem involves finding the volume of a cylindrical can given its diameter. The solid is a right circular cylinder with diameter 10 cm and height 12 cm. Since the volume formula V = πr²h requires radius, we must first convert: radius = diameter/2 = 10/2 = 5 cm. Applying the formula: V = π(5)²(12) = π(25)(12) = 300π cubic centimeters. This represents the can's total capacity. A common mistake is using diameter directly in the formula, giving π(10)²(12) = 1200π, which is four times too large. Always convert diameter to radius before applying cylinder volume formulas.

2

A concrete pillar is a cylinder with diameter $12\text{ ft}$ and height $5\text{ ft}$. What is the volume of the solid?

$180\pi\text{ ft}^3$

$360\pi\text{ ft}^3$

$720\pi\text{ ft}^3$

$180\pi\text{ ft}^2$

Explanation

This problem requires finding the volume of a concrete pillar. The solid is a cylinder with diameter 12 ft and height 5 ft. The volume formula for a cylinder is V = πr²h, but we must first convert diameter to radius: r = 12/2 = 6 ft. Applying the formula: V = π(6)²(5) = π(36)(5) = 180π ft³. The volume represents the amount of concrete needed to form the pillar. A common mistake is using diameter directly in the formula instead of radius, which would give π(12)²(5) = 720π ft³. Always convert diameter to radius by dividing by 2 before applying cylinder volume formulas.

3

An ice cream cone is a right circular cone with radius $4\text{ cm}$ and height $12\text{ cm}$. Which calculation correctly applies the volume formula for the cone?

$\frac{1}{3}\pi(4)^2(12)$

$\pi(4)^2(12)$

$2\pi(4)(12)$

$4\pi(12)$

Explanation

Solving problems with volume formulas involves calculating the space occupied by three-dimensional solids using appropriate mathematical expressions. The solid in this problem is a right circular cone. The correct volume formula for a cone is V = (1/3)πr²h, where r is the radius and h is the height. Applying the formula with r = 4 cm and h = 12 cm gives the expression (1/3)π(4)²(12), matching choice B. This expression correctly computes the volume by accounting for the conical shape's one-third factor of a cylinder's volume. A common distractor misconception is using the cylinder volume formula without the one-third, as in choice A, which overestimates the volume. To transfer this strategy, always identify the solid as a cone before selecting and applying the volume formula.

4

A solid metal sphere has radius $6\text{ cm}$. Which calculation correctly applies the volume formula?

$\pi(6^2)(6)$

$(4\pi)(6^2)$

$\frac{1}{3}\pi(6^2)(6)$

$\frac{4}{3}\pi(6^3)$

Explanation

This problem asks which calculation correctly applies the volume formula for a sphere. The solid is a sphere with radius 6 cm. The volume formula for a sphere is V = (4/3)πr³, where r is the radius. The correct calculation is V = (4/3)π(6³) = (4/3)π(216). This gives the volume in cubic centimeters. Option C represents the formula for a cylinder (πr²h), which is incorrect for a sphere. To solve volume problems accurately, first identify the three-dimensional shape before selecting the appropriate formula.

5

A cylindrical candle has radius $5\text{ cm}$ and height $12\text{ cm}$. Which expression represents the volume?

$2\pi(5)(12)$

$\frac{4}{3}\pi(5^3)$

$\frac{1}{3}\pi(5^2)(12)$

$\pi(5^2)(12)$

Explanation

This problem asks which expression represents the volume of a cylindrical candle. The solid is a cylinder with radius 5 cm and height 12 cm. The volume formula for a cylinder is V = πr²h, where r is the radius and h is the height. The correct expression is π(5²)(12) or π(25)(12). This formula gives the volume in cubic centimeters. Option A represents the lateral surface area formula (2πrh), not volume. To find volume, always use formulas that multiply three dimensions or include squared terms for circular shapes.

6

A cone and a cylinder have the same base radius and height. If the volume of the cylinder is $$432\pi$$ cubic centimeters, what is the volume of the cone?

$$72\pi$$ cubic centimeters

$$216\pi$$ cubic centimeters

$$324\pi$$ cubic centimeters

$$144\pi$$ cubic centimeters

Explanation

The volume of a cylinder is $$V_{cylinder} = \pi r^2 h$$ and the volume of a cone is $$V_{cone} = \frac{1}{3}\pi r^2 h$$. Since they have the same base radius and height, $$V_{cone} = \frac{1}{3} V_{cylinder} = \frac{1}{3} \times 432\pi = 144\pi$$ cubic centimeters. Choice A ($$72\pi$$) represents $$\frac{1}{6}$$ of the cylinder volume. Choice C ($$216\pi$$) represents $$\frac{1}{2}$$ of the cylinder volume. Choice D ($$324\pi$$) represents $$\frac{3}{4}$$ of the cylinder volume.

7

A party cone is filled with candy. The cone has radius $6\text{ cm}$ and height $10\text{ cm}$. Which calculation correctly applies the volume formula?

$V=\tfrac{4}{3}\pi(6)^3$

$V=\tfrac{1}{3}\pi(6)^2(10)$

$V=2\pi(6)(10)+2\pi(6)^2$

$V=\pi(6)^2(10)$

Explanation

This problem involves finding the volume of a party cone filled with candy. The solid is a cone with radius 6 cm and height 10 cm. The volume formula for a cone is V = (1/3)πr²h, where r is the radius and h is the height. The correct calculation is V = (1/3)π(6)²(10), which matches option B. This formula gives one-third the volume of a cylinder with the same base and height. Option A incorrectly uses the cylinder formula without the 1/3 factor, while option D uses the surface area formula. To solve volume problems correctly, first identify whether the solid is a cone, cylinder, or sphere before selecting the appropriate formula.

8

A spherical balloon has radius $7\text{ in}$. What is the volume of the solid?

$\tfrac{4}{3}\pi(7)^3\text{ in}^2$

$\tfrac{4}{3}\pi(7)^3\text{ in}^3$

$\pi(7)^2\text{ in}^3$

$\tfrac{1}{3}\pi(7)^2\text{ in}^3$

Explanation

This problem asks for the volume of a spherical balloon. The solid is a sphere with radius 7 inches. The volume formula for a sphere is V = (4/3)πr³, where r is the radius. Applying the formula: V = (4/3)π(7)³ = (4/3)π(343) in³. The correct answer includes the proper cubic units (in³) for volume. Option B incorrectly uses πr², which is the area of a circle, not the volume of a sphere, while option D has the wrong units (in² instead of in³). When calculating sphere volume, remember to cube the radius and multiply by (4/3)π, not just π.

9

A cylindrical container with radius 5 cm and height 20 cm is filled with water to a depth of 15 cm. A solid sphere is completely submerged in the water, causing the water level to rise to exactly 18 cm. What is the radius of the sphere?

$$\sqrt[3]{\frac{300}{4\pi}}$$ cm

$$\sqrt[3]{\frac{225}{4\pi}}$$ cm

$$\sqrt[3]{\frac{225}{4}}$$ cm

$$\sqrt[3]{\frac{75}{\pi}}$$ cm

Explanation

The volume of water displaced equals the rise in water level times the base area of the cylinder. The water level rises from 15 cm to 18 cm, a rise of 3 cm. Volume displaced = $$\pi(5)^2(3) = 75\pi$$ cubic cm. This equals the volume of the sphere: $$\frac{4}{3}\pi r^3 = 75\pi$$. Solving: $$\frac{4}{3}r^3 = 75$$, so $$r^3 = \frac{75 \times 3}{4} = \frac{225}{4}$$, giving $$r = \sqrt[3]{\frac{225}{4}}$$ cm. Choice A omits the $$\pi$$ cancellation step. Choice B results from incorrectly setting $$\frac{4}{3}\pi r^3 = 75$$ instead of $$75\pi$$. Choice D uses an incorrect volume calculation.

10

An ice cream cone is a right circular cone with radius $4\text{ cm}$ and height $9\text{ cm}$. Which expression represents the volume of the cone?

$\frac{1}{3}\pi(4^2)(9)$

$2\pi(4)(9)$

$\frac{4}{3}\pi(4^3)$

$\pi(4^2)(9)$

Explanation

This problem asks for the volume expression of a cone-shaped ice cream cone. The solid is a right circular cone with radius 4 cm and height 9 cm. The volume formula for a cone is V = (1/3)πr²h, where r is the radius and h is the height. The correct expression is (1/3)π(4²)(9), which represents one-third of the volume of a cylinder with the same base and height. This formula accounts for the cone's tapering shape from base to apex. A common mistake is using the cylinder formula π(4²)(9), forgetting the factor of 1/3. Remember that a cone's volume is always one-third of a cylinder with the same dimensions.

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