Area & Volume
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PSAT Math › Area & Volume
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?
$72\text{ cm}^2$
$132\text{ cm}^2$
$44\text{ cm}^2$
$66\text{ cm}^2$
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.
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?
$132\text{ m}^2$
$44\text{ m}^2$
$36\text{ m}^2$
$66\text{ m}^2$
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.
A circle is inscribed in a square so that it touches all four sides of the square. The diameter of the circle is $10\text{ cm}$. What is the area of the region inside the square but outside the circle? Use $\pi=3.14$.
$21.5\text{ cm}^2$
$100\text{ cm}^2$
$50\text{ cm}^2$
$78.5\text{ cm}^2$
Explanation
The question asks for the area inside a square but outside an inscribed circle with diameter 10 cm, in square centimeters, using π=3.14. The formulas needed are square area (side²) and circle area (πr²), with side equal to diameter, 10 cm. Square area: 10 × 10 = 100 cm². Circle radius is 5 cm, area: 3.14 × 25 = 78.5 cm². Remaining area: 100 - 78.5 = 21.5 cm². A common error is using radius for square side, leading to 25 cm² square minus smaller area. When finding regions between shapes, calculate each area separately and subtract, verifying units like cm².
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?
$12{,}000\text{ cm}^3$
$60{,}000\text{ cm}^3$
$6{,}000\text{ cm}^3$
$120{,}000\text{ cm}^3$
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.
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?
$54\text{ in}^2$
$108\text{ in}^2$
$252\text{ in}^2$
$216\text{ in}^2$
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.
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?
$75\text{ cm}^2$
$60\text{ cm}^2$
$150\text{ cm}^2$
$45\text{ cm}^2$
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.
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?
$91\text{ in}^2$
$26\text{ in}^2$
$182\text{ in}^2$
$52\text{ in}^2$
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.
A rectangular prism has dimensions $2.5\text{ ft}$ by $4\text{ ft}$ by $6\text{ ft}$. What is its volume?
$12.5\text{ ft}^3$
$50\text{ ft}^3$
$60\text{ ft}^3$
$25\text{ ft}^3$
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.
A cylindrical water tank has radius $3\text{ m}$ and height $10\text{ m}$. What is the volume of the tank? (Use $\pi$ in your answer.)
$30\pi\text{ m}^3$
$180\pi\text{ m}^3$
$90\pi\text{ m}^3$
$9\pi\text{ m}^3$
Explanation
We need to find the volume of a cylinder with radius 3 m and height 10 m. The volume formula for a cylinder is V = πr²h, where r is the radius and h is the height. Substituting the given values: V = π(3)²(10) = π(9)(10) = 90π m³. Common mistakes include using diameter instead of radius or forgetting to square the radius. When working with π, leave it in symbolic form unless asked to approximate.
On a coordinate plane, a rectangle has vertices $(-2,1)$, $(4,1)$, $(4,6)$, and $(-2,6)$. What is the area of the rectangle?
20 square units
30 square units
36 square units
25 square units
Explanation
The question asks for the area of a rectangle with vertices at (-2,1), (4,1), (4,6), and (-2,6) on a coordinate plane, with the answer in square units. The formula for the area of a rectangle is length × width, determined from the differences in x- and y-coordinates, ensuring units are consistent as unitless here. The width is the change in x: 4 - (-2) = 6 units, and the height is the change in y: 6 - 1 = 5 units. Therefore, area = 6 × 5 = 30 square units. A key error is miscalculating the height as 6 units by subtracting y-coordinates incorrectly, leading to 6 × 6 = 36. Another mistake might be confusing the shape with a non-rectangle and using a different formula. As a test-taking strategy, plot the points mentally to confirm the shape and double-check coordinate differences.