Area & Volume

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PSAT Math › Area & Volume

Questions 1 - 10
1

A trapezoid has bases of lengths $14\text{ cm}$ and $8\text{ cm}$. Its height is $6\text{ cm}$. What is the area of the trapezoid?

$66\text{ cm}^2$

$44\text{ cm}^2$

$72\text{ cm}^2$

$132\text{ cm}^2$

Explanation

The question asks for the area in square centimeters of a trapezoid with bases 14 cm and 8 cm, and height 6 cm. The formula for the area of a trapezoid is (1/2) × (base1 + base2) × height. Substitute the values: (1/2) × (14 + 8) × 6 = (1/2) × 22 × 6. Calculate 22 × 6 = 132, then (1/2) × 132 = 66 cm², with squared units for area. A common error is using only one base or forgetting the 1/2 factor. When working with trapezoids, emphasize selecting the correct formula and verifying unit consistency.

2

A trapezoid has bases of lengths $14\text{ m}$ and $8\text{ m}$. Its height is $6\text{ m}$. What is the area of the trapezoid?

$66\text{ m}^2$

$36\text{ m}^2$

$132\text{ m}^2$

$44\text{ m}^2$

Explanation

The question asks for the area of a trapezoid with bases 14 m and 8 m, and height 6 m, in square meters. The formula needed is the area of a trapezoid, (1/2) × (sum of bases) × height. Substitute the values: (1/2) × (14 + 8) × 6 = (1/2) × 22 × 6 = 11 × 6 = 66 m². This calculation directly gives the area without further steps. A common error is forgetting the (1/2) factor, resulting in 132 m², or using only one base. For trapezoid areas, always average the bases before multiplying by height, and confirm units like meters are squared for area.

3

A rectangular prism has dimensions $0.5\text{ m}$ by $40\text{ cm}$ by $30\text{ cm}$. What is the volume of the prism in cubic centimeters?

$60{,}000\text{ cm}^3$

$12{,}000\text{ cm}^3$

$6{,}000\text{ cm}^3$

$120{,}000\text{ cm}^3$

Explanation

The question asks for the volume in cubic centimeters of a rectangular prism with dimensions 0.5 m by 40 cm by 30 cm. The formula for the volume of a rectangular prism is length × width × height, requiring consistent units. Convert 0.5 m to 50 cm for consistency in centimeters. Then, volume = 50 × 40 × 30 = 2000 × 30 = 60,000 cm³, noting cubic units for volume. A key error is neglecting unit conversion, leading to incorrect multiplication. Always convert to the requested units before applying the formula to ensure accuracy.

4

A rectangular prism has dimensions $2.5\text{ ft}$ by $4\text{ ft}$ by $6\text{ ft}$. What is its volume?

$25\text{ ft}^3$

$50\text{ ft}^3$

$12.5\text{ ft}^3$

$60\text{ ft}^3$

Explanation

To find the volume of a rectangular prism with dimensions 2.5 ft × 4 ft × 6 ft, we use the formula V = length × width × height. Substituting the values: V = 2.5 × 4 × 6 = 10 × 6 = 60 ft³. When multiplying decimals, it's helpful to first multiply 2.5 × 4 = 10, then multiply by 6. Common errors include miscalculating with the decimal or confusing surface area formulas with volume formulas.

5

A cylinder has radius $4\text{ cm}$ and height $15\text{ cm}$. What is the volume of the cylinder? Use $\pi$ in your answer.

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

$60\pi\text{ cm}^3$

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

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

Explanation

The question asks for the volume in cubic centimeters of a cylinder with radius $4 \text{ cm}$ and height $15 \text{ cm}$, including $\pi$ in the answer. The formula for the volume of a cylinder is $V = \pi r^2 h$, where $r$ is radius and $h$ is height. Substitute $r = 4 \text{ cm}$ and $h = 15 \text{ cm}$ into the formula: $V = \pi(4)^2 \times 15 = \pi \times 16 \times 15$. Calculate $16 \times 15 = 240$, so $V = 240\pi \text{ cm}^3$, ensuring units are consistent in centimeters for all measurements. A key error might be using diameter instead of radius or forgetting to square the radius. When dealing with volumes, always confirm the formula and unit consistency to avoid calculation mistakes.

6

A right triangle has legs of length $9\text{ cm}$ and $12\text{ cm}$. A rectangle is formed using the triangle’s hypotenuse as the rectangle’s length and using a width of $5\text{ cm}$. What is the area of the rectangle?

$60\text{ cm}^2$

$45\text{ cm}^2$

$150\text{ cm}^2$

$75\text{ cm}^2$

Explanation

First, we need to find the hypotenuse of the right triangle with legs 9 cm and 12 cm using the Pythagorean theorem: c² = a² + b². So c² = 9² + 12² = 81 + 144 = 225, giving c = 15 cm. The rectangle uses this hypotenuse (15 cm) as its length and has width 5 cm. Rectangle area = length × width = 15 × 5 = 75 cm². A common mistake is using one of the legs instead of the hypotenuse, or forgetting to apply the Pythagorean theorem.

7

A cylindrical water tank has radius $0.6\text{ m}$ and height $2.5\text{ m}$. What is the volume of the tank in cubic meters? Use $\pi=3.14$.

$4.710\text{ m}^3$

$1.413\text{ m}^3$

$2.826\text{ m}^3$

$7.065\text{ m}^3$

Explanation

The question asks for the volume of a cylindrical water tank in cubic meters. The formula needed is the volume of a cylinder, V = πr²h, where r is the radius and h is the height. Substitute the given values: r = 0.6 m, h = 2.5 m, and π = 3.14, so V = 3.14 × (0.6)² × 2.5. First, compute (0.6)² = 0.36, then 3.14 × 0.36 = 1.1304, and finally 1.1304 × 2.5 = 2.826 m³. This matches the calculation for option A. A key error might be using diameter instead of radius or forgetting to square the radius, leading to incorrect volumes. For volume problems, always verify units are consistent, such as meters for all dimensions, and double-check the formula application.

8

A triangular garden plot has vertices at $(0,0)$, $(8,0)$, and $(2,6)$ on a coordinate plane, where each unit represents 1 meter. What is the area of the garden plot?

$12\text{ m}^2$

$24\text{ m}^2$

$48\text{ m}^2$

$18\text{ m}^2$

Explanation

The question asks for the area of a triangular garden plot with vertices at (0,0), (8,0), and (2,6) on a coordinate plane where each unit is 1 meter, with the answer in square meters. The formula for the area of a triangle given vertices is (1/2) |x1(y2 - y3) + x2(y3 - y1) + x3(y1 - y2)|, or alternatively (1/2) base × height, with consistent meter units. Using base from (0,0) to (8,0) = 8 m and height = 6 m, area = (1/2) × 8 × 6 = 24 m². The shoelace formula confirms: (1/2) |0(0-6) + 8(6-0) + 2(0-0)| = (1/2) |48| = 24 m². A key error is using the wrong height, like distance from (2,6) to base incorrectly as 2 m, giving (1/2) × 8 × 2 = 8 m². Another mistake might be calculating perimeter instead, summing distances. As a test-taking strategy, choose the base as the longest side and drop a perpendicular for height to simplify calculations.

9

A trapezoid has bases of lengths $10\text{ in}$ and $16\text{ in}$ and height $7\text{ in}$. What is the area of the trapezoid?

$182\text{ in}^2$

$52\text{ in}^2$

$26\text{ in}^2$

$91\text{ in}^2$

Explanation

The area of a trapezoid with bases 10 in and 16 in and height 7 in is found using A = ½ × (b₁ + b₂) × h. Substituting values: A = ½ × (10 + 16) × 7 = ½ × 26 × 7 = 13 × 7 = 91 in². The key is to add the bases first (10 + 16 = 26), then multiply by height and divide by 2. Common mistakes include forgetting to divide by 2 or multiplying only one base by the height.

10

A right triangular sign has legs of lengths $9\text{ in}$ and $12\text{ in}$. The sign is painted on both sides. What is the total painted area of the sign?

$252\text{ in}^2$

$216\text{ in}^2$

$108\text{ in}^2$

$54\text{ in}^2$

Explanation

The question asks for the total painted area in square inches of a right triangular sign with legs 9 in and 12 in, painted on both sides. The formula for the area of a triangle is (1/2) × base × height, applied to one side and doubled for both. For one side, area = (1/2) × 9 × 12 = (1/2) × 108 = 54 in². For both sides, total = 2 × 54 = 108 in², with units squared for area. A common error is forgetting to account for both sides or using the hypotenuse incorrectly. In problems involving surfaces, confirm if multiple faces are included and handle units appropriately.

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