Correct Answer: B

Rationale: If 5 nurses can care for 20 patients, it means each nurse is responsible for 20/5 = 4 patients. To care for 40 patients, we divide the total patients by the number of patients each nurse can care for: 40/4 = 10 nurses. Therefore, 10 nurses are needed for 40 patients. Among the options, the closest number is 8 nurses, making it the correct answer. Choice A, 7 nurses, is insufficient. Choice C, 9 nurses, exceeds the required amount. Choice D, 10 nurses, matches the total number of nurses required, not the closest, making it incorrect.

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.

Correct Answer: A

Rationale: To determine the largest fraction, it's helpful to convert them to decimals for easier comparison. Converting the fractions to decimals gives: 3/8 = 0.375, 3/9 = 0.333, 3/6 = 0.5, and 3/7 ≈ 0.429. Therefore, 3/7 is the largest fraction among the given options. Choice B, 3/6, is actually equivalent to 3/6 = 0.5 which is greater than 3/7. Choices C and D are smaller fractions compared to 3/7, making them incorrect.

Correct Answer: B

Rationale: To calculate speed, divide the distance traveled by the time taken: 240 miles · 4 hours = 60 mph. Therefore, the correct answer is B. Choice A (50 mph) is incorrect as it results from an incorrect calculation. Choice C (55 mph) and D (75 mph) are also incorrect because they are not the correct result of dividing 240 miles by 4 hours.

Correct Answer: C

Rationale: The correct answer is 2 liters. There are 1,000 milliliters in a liter. Therefore, 2,000 milliliters is equal to 2 liters. Choice A is incorrect because it incorrectly doubles the conversion. Choice B is incorrect as it represents the amount in milliliters, not liters. Choice D is a duplicate of choice A, which is incorrect.