Correct Answer: A

Rationale: To find out how many cups of sugar are needed for 90 cookies when 4 cups make 120 cookies, set up a proportion: 4/120 = x/90. Cross multiply to get 120x = 4 * 90. Solve for x to find x = 360/120 = 3. Therefore, 3 cups of sugar are needed for 90 cookies. Choice B (2 cups), Choice C (1.5 cups), and Choice D (4 cups) are incorrect because they do not align with the correct proportion calculation. The correct calculation shows that 3 cups of sugar are required for 90 cookies, as the recipe proportionally reduces when making fewer cookies.

Correct Answer: A

Rationale: To subtract mixed numbers, subtract the whole numbers and fractions separately. If necessary, borrow from the whole number when the fraction in the minuend is smaller than the fraction in the subtrahend. The whole numbers are: 25 - 12 = 13. The fractions: 1/7 - 5/7. Since 1/7 is smaller, borrow 1 from 13, making it 12. Then convert 1 whole into 7/7, so the fraction becomes: (7/7 + 1/7) - 5/7 = 8/7 - 5/7 = 3/7. Thus, 25 1/7 - 12 5/7 = 12 3/7.

Correct Answer: A

Rationale: When adding fractions with the same denominator, you simply add the numerators while keeping the denominator the same. In this case, 7/21 + 10/21 = 17/21. Therefore, the correct answer is A. Choice B (15/21) is incorrect because it adds the numerators incorrectly. Choice C (9/21) is incorrect as it does not reflect the sum of the fractions provided. Choice D (10/21) is also incorrect as it does not represent the correct sum of the two fractions.

Correct Answer: C

Rationale: To multiply fractions, you multiply the numerators together and the denominators together. Calculating 4/9 x 1 & 4/5 x 2/5 gives you (4 x 1) / (9 x 1) & (4 x 2) / (5 x 5) = 4/9 & 8/25. Therefore, the correct answer is 8/25. Choices A, B, and D are incorrect because they do not result from the correct multiplication of the fractions provided.

Correct Answer: D

Rationale: To convert 0.45 to a percentage, you multiply by 100: 0.45 100 = 45%. Therefore, the correct answer is D. 45%. Choice A, 4.5%, is incorrect. This percentage would be equal to 0.045, not 0.45. Choice B, 0.045%, is also incorrect. It represents 0.045, not 0.45. Choice C, 0.45%, is very close to the correct answer but actually represents 0.0045, not 0.45.