Solving Problems with Volume Formulas
Help Questions
Geometry › Solving Problems with Volume Formulas
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?
$2\pi(4)(9)$
$\frac{1}{3}\pi(4^2)(9)$
$\pi(4^2)(9)$
$\frac{4}{3}\pi(4^3)$
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.
A cylindrical candle (radius $3\text{ cm}$, height $14\text{ cm}$) has a conical hole drilled straight down from the top. The hole is a cone with the same radius $3\text{ cm}$ and depth (height) $6\text{ cm}$. Which value represents the total volume of wax remaining?
$\pi(3)^2(14)+\tfrac{1}{3}\pi(3)^2(6)$
$2\pi(3)(14)+2\pi(3)^2-\pi(3)(6)$
$\pi(3)^2(14)-\tfrac{1}{3}\pi(3)^2(6)$
$\tfrac{1}{3}\pi(3)^2(14)-\pi(3)^2(6)$
Explanation
This problem requires finding the volume of wax in a candle with a conical hole. The solid is a cylinder (radius 3 cm, height 14 cm) minus a cone (same radius 3 cm, depth 6 cm). The volume formula requires subtracting: V = cylinder volume - cone volume = πr²h - (1/3)πr²h. Applying: V = π(3)²(14) - (1/3)π(3)²(6) = 126π - 18π = 108π cm³. The subtraction accounts for the removed wax from the conical hole. Option C incorrectly adds the volumes instead of subtracting. When dealing with composite solids involving removal, subtract the volume of the removed portion from the original solid.
A cylindrical can has diameter $10\text{ cm}$ and height $12\text{ cm}$. What is the volume of the can in cubic centimeters?
$120\pi\text{ cm}^3$
$300\pi\text{ cm}^3$
$240\pi\text{ cm}^3$
$600\pi\text{ cm}^3$
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.
A cylindrical candle has radius $5\text{ cm}$ and height $12\text{ cm}$. Which expression represents the volume?
$\frac{4}{3}\pi(5^3)$
$2\pi(5)(12)$
$\pi(5^2)(12)$
$\frac{1}{3}\pi(5^2)(12)$
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.
A square pyramid has a base side length of $8\text{ m}$ and height $15\text{ m}$. What is the volume of the pyramid in cubic meters?
$256\text{ m}^3$
$960\text{ m}^3$
$160\text{ m}^3$
$320\text{ m}^3$
Explanation
This problem requires finding the volume of a square pyramid. The solid is a square pyramid with base side length 8 m and height 15 m. The volume formula for a pyramid is V = (1/3)Bh, where B is the base area and h is the height. For a square base, B = s² = 8² = 64 m². Applying the formula: V = (1/3)(64)(15) = (1/3)(960) = 320 cubic meters. A common error is forgetting the factor of 1/3, which would give 960 m³ instead. When solving pyramid problems, remember that the volume is always one-third of the base area times the height.
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?
$\frac{1}{3}\pi(4)^2(12)$
$\pi(4)^2(12)$
$4\pi(12)$
$2\pi(4)(12)$
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.
A right square pyramid has a square base with side length $6\text{ m}$ and height $9\text{ m}$. What is the volume of the pyramid?
$180\text{ m}^3$
$108\text{ m}^3$
$216\text{ m}^2$
$324\text{ m}^3$
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 square pyramid. The correct volume formula for a pyramid is V = (1/3) B h, where B is the base area and h is the height. Applying the formula with base side 6 m (B = 36 m²) and h = 9 m gives V = (1/3)(36)(9) = 108 m³, matching choice B. This result correctly accounts for the pyramidal shape's volume being one-third of a prism with the same base and height. A common distractor misconception is omitting the one-third factor, as in calculating 36 × 9 = 324 m³ like choice A. To transfer this strategy, always identify the solid as a pyramid before selecting and applying the volume formula.
A cylindrical candle has radius $2.5\text{ in}$ and height $8\text{ in}$. Which expression represents the volume of the candle?
$\pi(2.5)^2(8)$
$2\pi(2.5)(8)$
$\pi(2.5)(8)$
$\frac{1}{3}\pi(2.5)^2(8)$
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 cylinder. The correct volume formula for a cylinder is V = πr²h, where r is the radius and h is the height. Applying the formula with r = 2.5 in and h = 8 in gives the expression π(2.5)²(8), matching choice A. This expression accurately computes the volume based on the cylindrical dimensions. A common distractor misconception is using the lateral surface area formula, as in choice B, which calculates 2πr h instead of volume. To transfer this strategy, always identify the solid as a cylinder before selecting and applying the volume formula.
A cylindrical water tank has an inside radius of $3\text{ m}$ and an inside height of $10\text{ m}$. What is the volume of water the tank can hold when full?
$90\pi\text{ m}^3$
$60\pi\text{ m}^3$
$180\pi\text{ m}^2$
$78\pi\text{ m}^3$
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 cylinder. The correct volume formula for a cylinder is $V = \pi r^2 h$, where r is the radius and h is the height. Applying the formula with $r = 3 \text{ m}$ and $h = 10 \text{ m}$ gives $V = \pi(3)^2 (10) = 90\pi \text{ m}^3$. This result represents the maximum capacity of water the tank can hold when full, matching choice B. A common distractor misconception is using the surface area formula, such as choice D, which calculates $2\pi r h + 2\pi r^2$ instead of volume. To transfer this strategy, always identify the solid as a cylinder before selecting and applying the volume formula.
A cylindrical juice can has radius $3\text{ cm}$ and height $12\text{ cm}$. Which claim about the volume is NOT justified?
The volume is $108\pi\text{ cm}^3$.
The volume is proportional to the height.
The volume is $\pi(3)^2(12)\text{ cm}^3$.
The volume is $2\pi(3)(12)\text{ cm}^3$.
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 cylinder. The correct volume formula for a cylinder is V = $\pi r^2 h$, where r is the radius and h is the height. Applying the formula with r = 3 cm and h = 12 cm gives V = $\pi(3)^2 (12) = 108\pi$ cm³, which shows claims A and B are justified while D is a valid property. However, claim C uses $2\pi r h$, the lateral surface area, incorrectly as volume, making it not justified and matching choice C. A common distractor misconception is confusing volume with surface area formulas, as seen in choice C. To transfer this strategy, always identify the solid as a cylinder before evaluating claims about its volume.