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 compare who ate more of their meal, we need to convert the fractions to the same format. John ate 75% of his lunch, which is equivalent to 3/4. Sally ate 5/8 of her lunch. Comparing 3/4 to 5/8, we find that 3/4 is greater than 5/8. Therefore, John ate more of his meal than Sally. Choice B, John, is the correct answer. Choices A, C, and D are incorrect because John consumed 3/4 of his lunch, which is more than 5/8 that Sally consumed, making him the one who ate more of his meal.

Correct Answer: A

Rationale: To subtract 2 5/8 from 7/8, first, convert 7/8 to an equivalent fraction with the same denominator as 2 5/8, which is 8. 7/8 equals 1 whole and 1/8. Subtracting 1 whole from 2 whole results in 1 whole, and subtracting 1/8 from 5/8 gives 4/8 or 1/2. Therefore, the answer is 1 1/2, which simplifies to 1 3/4. Choice B, 2, is incorrect as it doesn't represent the correct result of the subtraction. Choice C, 1, is incorrect as it doesn't account for the fractional part of the answer. Choice D, 2 & 1/2, is incorrect as it doesn't match the calculated result of 1 3/4.

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 add fractions, find a common denominator, which in this case is 40. Convert each fraction to have the common denominator: 7/8 = 35/40, 9/10 = 36/40, and 6/5 = 48/40. Add these fractions to get 119/40. Simplify this improper fraction to a mixed number, which is 3 & 39/40. Choice B and C are incorrect as they do not represent the sum of the fractions. Choice D is incorrect; the whole number part should be 3, not 2.