Correct Answer: C

Rationale: If 80% of the class passed with a 75 or higher, and that equals 24 students, you can set up a proportion to find the total number of students in the class. Since 80% is equal to 24 students, 100% (the whole class) would be equal to (24/80) x 100 = 30 students. Therefore, the total number of students in the whole class is 30 / 80 x 100 = 36. Choice A (18) is incorrect as it does not match the calculation based on the information given. Choice B (30) is incorrect because it represents the intermediate calculation but not the total number of students in the class. Choice D (60) is incorrect as it is double the correct answer and does not align with the given information.

Correct Answer: C

Rationale: Latoya practices her flute for 15 minutes every day. In two weeks (14 days), the total time spent practicing can be calculated as 15 minutes/day * 14 days = 210 minutes. To convert 210 minutes to hours, divide by 60 (since there are 60 minutes in an hour): 210 / 60 = 3 hours 30 minutes. Therefore, Latoya spends 3 hours 30 minutes practicing her flute over a period of two weeks. Choices A, B, and D are incorrect because they do not accurately calculate the total time Latoya spends practicing over two weeks.

Correct Answer: C

Rationale: To find the surface area of the cylinder, calculate the lateral surface area using the formula 2πrh, where r is the radius (half of the diameter) and h is the height. Substituting the values, we get 2 * π * 1 * 3 = 6π square meters. Since each can covers 10 sq m, divide the total surface area by the coverage area per can: 6π / 10 ≈ 1.9 cans. Since you can't buy a fraction of a can, you would need to round up, so you would need 2 cans to cover the entire exterior surface. Therefore, you would need 2 * 6 = 12 cans in total. Choices A, B, and D are incorrect as they do not consider the correct surface area calculation or the rounding up to the nearest whole number of cans required.

Correct Answer: A

Rationale: There are 1,000 milliliters in a liter. To convert 2,500 milliliters to liters, you divide by 1,000: 2,500 milliliters / 1,000 = 2.5 liters. Therefore, choice A, '2.5 liters,' is the correct answer. Choice B, '25 liters,' is incorrect as it would be the result if you mistakenly multiplied instead of dividing. Choice C, '250 liters,' is incorrect as it is 100 times the correct answer. Choice D, '25,000 liters,' is significantly higher and not a conversion error but an order of magnitude error.

Correct Answer: D

Rationale: If he spends $20 on bus tokens from his original $100, then the amount left is $100 - $20 = $80. The remaining 90% of $80 is calculated as $80 + 0.90 * $80 = $80 + $72 = $89.30. Therefore, the correct answer is $89.30. Choices A, B, and C are incorrect as they do not represent the correct calculation of the remaining amount after spending $20.