Correct Answer: A

Rationale: To add fractions with different denominators, find a common denominator. In this case, the common denominator of 4 and 8 is 8. Convert 1/4 to 2/8, then add it to 3/8. The sum is 5/8. Choice B (7/12) is incorrect as it is the result of adding 1/3 + 1/4. Choice C (2/3) is incorrect as it is the result of adding 3/8 + 1/4. Choice D (1/2) is incorrect as it is the result of adding 1/4 + 1/4.

Correct Answer: C

Rationale: To find the total surface area of the rectangular box, calculate the area of each side and sum them up. The areas of the sides are: 2(40x30) + 2(40x25) + 2(30x25) = 2400 + 2000 + 1500 = 5900 sq cm. Convert this to square meters by dividing by 10,000: 5900/10,000 = 0.59 sq m. Since one sheet covers 0.5 sq m, you would need 2 sheets to cover the box fully, which equals 1 sq m. Therefore, the correct answer is 1.2 sq m. Choice A (0.3 sq m) is too small for the dimensions provided. Choice B (0.6 sq m) is incorrect as it doesn't match the calculated surface area. Choice D (1.8 sq m) is too high for the surface area of the box.

Correct Answer: A

Rationale: The correct answer is A: 10 pounds. There are 16 ounces in a pound. To convert 160 ounces to pounds, you need to divide 160 by 16, which equals 10 pounds. Choice B, 8 pounds, is incorrect because it does not account for the correct conversion factor. Choice C, 5 pounds, is incorrect as it is not the result of dividing 160 by 16. Choice D, 12 pounds, is incorrect as it overestimates the conversion.

Correct Answer: A

Rationale: The correct answer is A, 50%. A standard six-sided die has three even numbers (2, 4, 6) out of six possible outcomes. The probability of rolling an even number is therefore 3 out of 6, which simplifies to 50%. Choices B, C, and D are incorrect because they do not accurately reflect the probability of rolling an even number on a six-sided die.

Correct Answer: A

Rationale: The correct subtraction is 12.02 - 9.99 = 2.03. Therefore, the correct answer is A. Choice B, 2.21, is incorrect as it does not result from the given subtraction. Choice C, 3.17, is also incorrect. Choice D, 7.97, is incorrect as well. Thus, A is the only correct answer.