Correct Answer: A

Rationale: To determine how much board Alan needs to cut off, subtract the length of the table from the length of the board: 7 7/8 - 6 1/2 = 1 3/8. Therefore, Alan needs to cut off 1 3/8 feet from the board. Choice A is correct. Choice B (2) is incorrect because the subtraction result is 1 3/8, not 2. Choice C (7/8) is incorrect as it represents only the fraction part of the answer, not the whole amount. Choice D (3/4) is incorrect as it is a different fraction value than the result of the subtraction.

Correct Answer: A

Rationale: To calculate the total number of newspapers sold each day, add the sales for each language: 25 (English) + 1 (French) + 16 (Korean) + 16 (Japanese) + 22 (Russian) = 80. Multiply this by the number of language varieties (10) to get the total number of newspapers sold: 80 x 10 = 800. Therefore, the kiosk sells 800 newspapers each day, not 368 as erroneously stated. The correct answer is 800 papers.

Correct Answer: A

Rationale: To add 12 1/21 and 3 1/3, first add the whole numbers: 12 + 3 = 15. Then, add the fractions: 1/21 + 1/3. To find a common denominator, multiply 21 by 3 to get 63. Convert 1/21 to an equivalent fraction with a denominator of 63 by multiplying the numerator and denominator by 3, resulting in 3/63. Now add 3/63 (equivalent to 1/21) and 21/63 (equivalent to 1/3) to get 24/63. Simplifying 24/63 gives 8/21. Therefore, the sum is 15 8/21. Choices B, C, and D are incorrect because they do not result from the correct addition of the given numbers and fractions.

Correct Answer: B

Rationale: To solve the proportion 0.1:10=x:400, first, simplify the left side to 1:100. Then, set up the proportion as 1:100=x:400. Cross multiply to get x = 4. Therefore, the correct answer is B. Choice A (5) is incorrect because it does not match the calculated value of x. Choice C (50) is incorrect as it is not the result of solving the proportion provided. Choice D (25) is incorrect as it does not align with the correct calculation of x.

Correct Answer: B

Rationale: To determine the largest number among the given decimals, compare them. 0.68 is the largest number as it is greater than 0.667, 0.6, and 0.0688. The correct answer is 0.68 because it has the highest value. The other options are smaller: 0.667 is less than 0.68, 0.6 is less than 0.68, and 0.0688 is significantly smaller than 0.68.