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. A lampshade is shaped like a frustum of a cone, with base diameters of 20cm and 10cm and a height of 15cm. What is its volume?

Correct answer: C

Rationale: To find the volume of the frustum of a cone, divide it into two cones and calculate their volumes separately. The formula for the volume of a cone frustum involves the radii of both bases and the height. The volume of the frustum cone can be calculated as V = 1/3 * π * h * (R^2 + r^2 + R * r), where R is the larger radius, r is the smaller radius, and h is the height. Substituting the values, V = 1/3 * π * 15 * (10^2 + 20*10 + 20^2) = 1875 cu cm. Therefore, the correct answer is 1875 cu cm. Choice A, B, and D are incorrect as they do not correspond to the correct calculation of the frustum's volume.

3. If 3 nurses can care for 15 patients, how many nurses are needed for 25 patients?

Correct answer: B

Rationale: To determine how many nurses are needed for 25 patients, set up a proportion: 3 nurses / 15 patients = x nurses / 25 patients. Cross multiply to solve for x: 3 * 25 = 15 * x. This simplifies to 75 = 15x. Divide both sides by 15 to find x = 5. Therefore, 5 nurses are needed for 25 patients. Choices A, C, and D are incorrect as they do not correspond to the correct calculation based on the given proportion.

4. What is 0.9 divided by 3?

Correct answer: C

Rationale: To find the result of dividing 0.9 by 3, we perform the division operation, which equals 0.3. Therefore, the correct answer is 0.3. Choice A (0) is incorrect as the result is not zero, but 0.3. Choice B (3) is incorrect as 0.9 divided by 3 is not 3 but 0.3. Choice D (9) is incorrect as 0.9 divided by 3 is not 9 but 0.3.

5. A label states 1 mil contains 500 mg. How many mils are there if there are 1.5 grams?

Correct answer: C

Rationale: To calculate the number of mils, first, convert 1.5 grams to milligrams (1.5 grams = 1500 mg). Then, since 1 mil contains 500 mg, divide 1500 mg by 500 mg/mil, resulting in 3 mils required to contain 1.5 grams of substance. Choice A, 9, is incorrect because it miscalculates the conversion. Choice B, 2, is incorrect as it does not consider the correct conversion factor. Choice D, 5, is incorrect as it also miscalculates the conversion.

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