Correct Answer: A

Rationale: To subtract mixed numbers, first subtract the fractions: 1/8 - 1/2 = -3/8. Then, subtract the whole numbers: 12 - 9 = 3. Combine the whole number and fraction: 3 - 3/8 = 2 5/8. Therefore, the correct answer is A. Choice B is incorrect because it does not reflect the correct subtraction of the fractions. Choices C and D are incorrect as they do not result from the correct subtraction process outlined above.

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: D

Rationale: To convert ounces to pounds, you need to know that there are 16 ounces in a pound. Therefore, to find out how many pounds are in 144 ounces, you divide 144 by 16, which equals 9 pounds. Choice A, 12 pounds, is incorrect because it does not correctly divide the number of ounces by the conversion factor. Choices B and C, 10 pounds and 8 pounds respectively, are also incorrect as they do not utilize the correct conversion factor to calculate the number of pounds in 144 ounces.

Correct Answer: B

Rationale: The correct factor to convert pounds to kilograms is 2.2. To perform the conversion, you need to divide the number of pounds by 2.2. Choice A (1.8) is incorrect as it's not the standard conversion factor. Choice C (2.5) and Choice D (2) are also incorrect factors for converting pounds to kilograms.

Correct Answer: D

Rationale: To find the total number of chapters, divide the total number of pages by the number of pages per chapter: 798 · 6 = 133 chapters. If he reads 2 chapters a day, it will take him 133 · 2 = 66.5 days to finish the book. Therefore, the correct answer is 66.5 days. Choice A is incorrect because it miscalculates the number of days required. Choices B and C are incorrect as they do not consider the correct calculation based on the given information.