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What is the surface area of the cylinder shown below?
- A. 602.9 cm²
- B. 904.3 cm²
- C. 1,408.7 cm²
- D. 1,507.2 cm²
Correct Answer: D
Rationale: The surface area of a cylinder can be calculated using the formula: S = 2πr² + 2πrh, where r is the radius and h is the height. Substituting the values for radius (12) and height (8) into the formula: S = 2π(12)² + 2π(12)(8). S = 2π(144) + 2π(96). S = 288π + 192π. S = 480π ≈ 1507.964. Therefore, the surface area of the cylinder is approximately 1507.2 square centimeters. Choice A, 602.9 cm², is incorrect as it is significantly lower than the correct value. Choice B, 904.3 cm², is also incorrect as it does not match the calculated surface area. Choice C, 1,408.7 cm², is incorrect as it does not align with the calculated value of the surface area.
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Curtis measured the temperature of water in a flask in his science class. The temperature of the water was 35 °C. He carefully heated the flask so that the temperature of the water increased by about 2 °C every 3 minutes. Approximately how much had the temperature of the water increased after 20 minutes?
- A. 10 °C
- B. 13 °C
- C. 15 °C
- D. 35 °C
Correct Answer: B
Rationale: To find the increase in temperature after 20 minutes, calculate how many 3-minute intervals are in 20 minutes (20 · 3 = 6.66, rounding to 7 intervals). Then, multiply the temperature increase per interval (2 °C) by the number of intervals (7 intervals), giving a total increase of 14 °C. Therefore, after 20 minutes, the temperature of the water would have increased by approximately 14 °C. Choice A, 10 °C, is incorrect as it underestimates the total increase. Choice C, 15 °C, is incorrect as it overestimates the total increase. Choice D, 35 °C, is incorrect as it represents the initial temperature of the water, not the increase in temperature.
On a floor plan drawn at a scale of 1:100, the area of a rectangular room is 30 cm². What is the actual area of the room?
- A. 30,000 cm²
- B. 300 m²
- C. 3,000 m²
- D. 30 m²
Correct Answer: D
Rationale: On a 1:100 scale drawing, each centimeter represents one meter. The area of the room in the scale drawing is 30 cm², which means the actual area is 30 m². Choice A (30,000 cm²) is incorrect as it doesn't account for the scale conversion. Choice B (300 m²) is incorrect because it multiplies the scale area directly by 10,000, which is not the correct conversion. Choice C (3,000 m²) is also incorrect as it applies the scale factor incorrectly.
Simplify the following expression: (2/7) · (5/6)
- A. 2/5
- B. 35/15
- C. 5/21
- D. 12/35
Correct Answer: D
Rationale: To divide fractions, you multiply the first fraction by the reciprocal of the second fraction. In this case, (2/7) · (5/6) becomes (2/7) (6/5) = 12/35. Therefore, the correct answer is 12/35. Choice A (2/5), choice B (35/15), and choice C (5/21) are incorrect because they do not correctly simplify the given expression.
Jeremy put a heavy chalk mark on the tire of his bicycle. His bike tire is 27 inches in diameter. When he rolled the bike, the chalk left marks on the sidewalk. Which expression can be used to best determine the distance, in inches, the bike rolled from the first mark to the fourth mark?
- A. 3(27π)
- B. 4π(27)
- C. (27 · 3)π
- D. (27 · 4)π
Correct Answer: A
Rationale: The distance traveled by the bike in one complete roll of the tire is equal to the circumference, which can be calculated using the formula C = πd, where d is the diameter. Given that the diameter of the bike tire is 27 inches, the circumference is obtained by multiplying the diameter by π. As the tire rolls from the first mark to the fourth mark, it completes three full rotations (one complete roll plus two more). Therefore, the total distance rolled is 3 times the circumference, which results in 3(27π). Choice A is correct. Choice B is incorrect as it incorrectly multiplies the diameter by 4π instead of multiplying the circumference by 4. Choices C and D are incorrect as they involve dividing the diameter by a number, which is not applicable in this context.
Chan receives a bonus from his job. He pays 30% in taxes, donates 30% to charity, and uses another 25% to pay off an old debt. He has $600 remaining. What was the total amount of Chan's bonus?
- A. $3,000
- B. $3,200
- C. $3,600
- D. $4,000
Correct Answer: D
Rationale: Chan has used 30% + 30% + 25% = 85% of his bonus, which leaves 15% remaining. Since 15% of his bonus is $600, you can find the total bonus amount by dividing $600 by 15% (or multiplying by 100/15), which equals $4,000. Therefore, the correct answer is $4,000. The other choices are incorrect because they do not accurately represent the total remaining amount after the specified deductions.