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. Express 2/5 as a decimal.

Correct answer: C

Rationale: To express 2/5 as a decimal, you divide the numerator (2) by the denominator (5). 2 ÷ 5 = 0.4. Choice A (0.2) is the decimal equivalent of 1/5, not 2/5. Choice B (0.25) is the decimal equivalent of 1/4, not 2/5. Choice D (2.5) is not the correct decimal equivalent of 2/5 as it is greater than 1.

3. Two buildings in downtown Chicago stand across the river. The first building is 1,700 feet tall and casts a shadow of 525 feet. If the second building is 1,450 feet tall, how long will its shadow be?

Correct answer: C

Rationale: To find the shadow of the second building, we use the ratio of heights to shadows: 1,700/525 = 1,450/x. Solving for x gives x = (525 × 1,450)/1,700 = 448.5. Therefore, the shadow of the second building will be approximately 448.5 feet long. Choice A (478 feet) is incorrect because it is not the result of the correct calculation. Choice B (455 feet) is incorrect as it does not match the accurate answer obtained through the calculation. Choice D (450 feet) is incorrect as it does not reflect the correct length of the shadow of the second building.

4. Solve for x: x/250 = 3/500.

Correct answer: C

Rationale: To solve for x, cross-multiply: x/250 = 3/500. This simplifies to x = 1.5. Therefore, the correct answer is 1.5. Choice A (150) is incorrect because it does not account for the division by 250. Choice B (25.5) is incorrect as it is not the correct result of the calculation. Choice D (60) is incorrect as it is not the correct result of the calculation either.

5. Richard wants to make 2.5 batches of sugar cookies. One batch calls for 1.75 cups of sugar. How many cups of sugar will Richard need for 2.5 batches?

Correct answer: A

Rationale: To calculate how much sugar Richard needs for 2.5 batches, multiply the amount of sugar needed for one batch (1.75 cups) by 2.5: 1.75 × 2.5 = 4.375  cups 1.75×2.5=4.375 cups Since the question is asking for the nearest whole number, 4.375 rounds to 4.

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