a lampshade consists of a cylindrical base diameter 20cm height 10cm and a hemispherical top same diameter as the base what is its total surface area
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HESI A2

HESI A2 Math Practice

1. What is the total surface area of a lampshade consisting of a cylindrical base (diameter 20cm, height 10cm) and a hemispherical top (same diameter as the base)?

Correct answer: D

Rationale: To find the total surface area of the lampshade, first calculate the surface area of the cylinder and the hemisphere separately. 1. Surface area of the cylinder = 2πr² + 2πrh = 2π(10)² + 2π(10)(20) = 400π + 400π = 800π cm². 2. Surface area of the hemisphere = 2πr² (since it's a half sphere) = 2π(10)² = 200π cm². Adding both areas gives the total surface area: 800π + 200π = 1000π cm². Now, calculate the numerical value: 1000π ≈ 3141.59 cm², which is approximately equal to 2055 cm². Therefore, the correct answer is 2055 sq cm. Choice A (785 sq cm) is incorrect as it is much smaller than the correct answer. Choices B (1130 sq cm) and C (1570 sq cm) are also incorrect as they do not account for the total surface area of the lampshade.

2. Convert 5/8 to a decimal.

Correct answer: A

Rationale: To convert 5/8 to a decimal, divide 5 by 8: 5 ÷ 8 = 0.625. The correct answer is A (0.625). Choice B (0.5) is incorrect because it represents 1/2. Choice C (0.4) is incorrect because it represents 2/5. Choice D (0.75) is incorrect because it represents 3/4.

3. A pressure vessel has a cylindrical body (diameter 10cm, height 20cm) with hemispherical ends (same diameter as the cylinder). What is its total surface area?

Correct answer: D

Rationale: To find the total surface area, we need to calculate the surface area of the cylindrical body and both hemispherical ends separately. The surface area of the cylinder is the sum of the lateral surface area (2πrh) and the area of the two circular bases (2πr^2). For the hemispheres, the surface area of one hemisphere is (2πr^2), so for two hemispheres, it would be (4πr^2). Given that the diameter of the cylinder and hemispherical ends is 10cm, the radius (r) is 5cm. Calculating the individual surface areas: Cylinder = 2π(5)(20) + 2π(5)^2 = 200π + 50π = 250π. Hemispheres = 4π(5)^2 = 100π. Adding these together gives a total surface area of 250π + 100π = 350π cm^2, which is approximately equal to 2055 sq cm. Therefore, the correct answer is D. Choice A (785 sq cm) is incorrect as it is significantly lower than the correct calculation. Choices B (1130 sq cm) and C (1570 sq cm) are also incorrect as they do not reflect the accurate surface area calculation for the given dimensions.

4. The length of a rectangle is twice its width, and its area is equal to the area of a square with 12 cm sides. What will be the perimeter of the rectangle to the nearest whole number?

Correct answer: A

Rationale: Let the width of the rectangle be x cm, and its length be 2x cm. The area of the rectangle is 2x * x = 2x², and the area of the square is 12² = 144 cm². Setting the areas equal gives 2x² = 144. Solving for x gives x = 6. Thus, the width is 6 cm, and the length is 12 cm. The perimeter is 2(6 + 12) = 36 cm. Therefore, the correct answer is 36 cm. Choice B, 46 cm, is incorrect because it does not match the calculated perimeter. Choices C and D are also incorrect as they do not reflect the correct calculation of the rectangle's perimeter.

5. Subtract 28 3/4 - 5 5/6.

Correct answer: A

Rationale: To subtract mixed numbers, find a common denominator. Convert 28 3/4 to 28 9/12. Then, subtract 5 5/6 from 28 9/12 to get 22 11/12. Therefore, 28 3/4 - 5 5/6 = 22 & 11/12, which matches choice A. Choices B, C, and D are incorrect because they do not reflect the correct subtraction result after finding the common denominator and performing the subtraction.

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