Correct Answer: A

Rationale: To find the amount of water left after 25% is used, you need to calculate 75% of the total water. 75% of 10 liters is 7.5 liters, which means that 7.5 liters of water are left. Therefore, the correct answer is A. Choice B (8 liters) is incorrect because this would be the total water remaining if 20% was used, not 25%. Choice C (6.5 liters) is incorrect as it does not account for the correct percentage of water left. Choice D (8.5 liters) is incorrect as it miscalculates the amount of water remaining after 25% is used.

Correct Answer: A

Rationale: To calculate the population increase, multiply the current population by 1 plus the percentage increase. So, 1,000 * 1.05 = 1,050 people. Therefore, the correct answer is A. Choice B (1,200 people) is incorrect because it represents a 20% increase from the current population, not 5%. Choice C (1,100 people) is incorrect as it reflects a 10% increase, not a 5% increase. Choice D (1,300 people) is incorrect, showing a 30% increase, which is not the scenario given.

Correct Answer: C

Rationale: To calculate the total time, first find the time for the first leg of the trip: 305 miles / 65 mph = 4.69 hours. Then, add the time for the second leg: 162 miles / 80 mph = 2.025 hours. Next, add the 15-minute stop in hours (15 minutes = 0.25 hours). Finally, add the times together: 4.69 hours + 2.025 hours + 0.25 hours = 6.965 hours, which rounds to 6.69 hours. Therefore, the correct answer is 6.69 hours. Choice A is incorrect because it does not account for the total driving time correctly. Choice B is incorrect as it does not include the time for the gas station stop. Choice D is wrong as it miscalculates the total time taken for the trip.

Correct Answer: B

Rationale: To find the number of girls in the class, we need to calculate 40% of the total number of students, which is 30. 40% of 30 is 0.40 * 30 = 12 girls. Therefore, there are 12 girls in the class. Choice A, 18 girls, is incorrect as it miscalculates the percentage. Choice C, 15 girls, is incorrect as it misrepresents the correct calculation. Choice D, 10 girls, is incorrect as it underestimates the number of girls in the class.

Correct Answer: A

Rationale: To find the percentage of staff certified and available, we first calculate the percentage of staff members not on vacation, which is 100% - 35% = 65%. Then, 20% of this group is certified to work, which is 20% of 65% = 0.20 * 65% = 13%. Therefore, Veronica has 13% of the staff certified and available to work. The correct answer is 0.13 (or 13%). Choice C (0.65) is incorrect because it represents the percentage of staff members not on vacation, not the percentage that is certified and available. Choice D (0.8) is incorrect as it is not the correct percentage of staff members certified and available. Choice B (0.13) is the correct answer, not choice A (0.07), as 0.07 represents 7%, not 13%.