Correct Answer: B

Rationale: To find the average time per mile, add the total time taken to cover all miles and then divide by the total miles run. The athlete ran 5 miles in 25 minutes and 3 miles in 15 minutes, totaling 8 miles in 40 minutes. Therefore, the average time per mile is 40 minutes · 8 miles = 5 minutes. Choice A, 7 minutes, is incorrect as it does not reflect the correct average time per mile. Choice C, 6.5 minutes, is incorrect since the calculation is not based on the given information. Choice D, 8.5 minutes, is incorrect as it does not represent the average time per mile for the entire run.

Correct Answer: A

Rationale: To convert yards to feet, you need to know that 1 yard is equal to 3 feet. Therefore, to convert yards to feet, you multiply the number of yards by 3. To convert feet to yards, you divide the number of feet by 3. Choice A correctly states that you should multiply yards by 3 to get feet and divide feet by 3 to get yards. Choices B, C, and D provide incorrect conversion factors, leading to inaccurate results.

Correct Answer: D

Rationale: To determine the greatest value among the given options, convert the fractions to decimal form. 2/11 is approximately 0.1818, 5.4 is a decimal itself, 13/3 is approximately 4.333, and 6.25 is a decimal. Comparing these values, 6.25 is the largest among them. Therefore, option D, 6.25, is the correct answer. Choices A, B, and C are smaller values compared to 6.25, making them incorrect answers.

Correct Answer: D

Rationale: To calculate a 30% increase from the current dosage of 270 mg, first find 30% of 270, which is 81 mg. Add this 81 mg increase to the original dosage of 270 mg to get the new dosage, which is 351 mg (270 mg + 81 mg = 351 mg). Therefore, the correct answer is 351 mg. Choice A (81 mg) is incorrect because this value represents only the calculated 30% increase, not the total dosage after the increase. Choice B (270 mg) is the original dosage and does not account for the 30% increase. Choice C (300 mg) is close to the correct answer but does not consider the precise 30% increase calculation, leading to an incorrect total dosage.

Correct Answer: C

Rationale: The baby's measured weight is the dependent variable as it depends on the time intervals.