Correct Answer: A

Rationale: The correct ratio of men to women is 3:4. To find the ratio, divide the number of men by the number of women: 12 men / 16 women = 3/4, which simplifies to 3:4. Therefore, in a class of 28 people with 12 men and 16 women, the ratio of men to women is 3:4. Choice B (4:7) is incorrect because it does not accurately reflect the given numbers of men and women in the class. Choice C (12:16) is incorrect as it represents the actual count of men and women, not the ratio. Choice D (1:2) is incorrect as it does not match the proportion of men to women in the class.

Correct Answer: B

Rationale: To find X in the given proportion 81:X::9:27, you can set up the equation 81/X = 9/27. Cross-multiplying gives 81 * 27 = 9 * X, which simplifies to 2187 = 9X. Dividing both sides by 9 results in X = 27. Therefore, the correct answer is B. Choice A (3) is incorrect as it does not satisfy the proportion. Choice C (21) is incorrect as it is not the correct value to make the proportion valid. Choice D (9) is incorrect as it does not align with the proportion provided.

Correct Answer: A

Rationale: To multiply decimals, align the numbers as whole numbers, multiply as if they were whole numbers, then adjust the decimal point in the final answer. When multiplying 0.67 by 0.09, the result is 0.0603. To get this result, multiply 67 by 9 to get 603, then adjust the decimal point two places to the left in the final product, resulting in 0.0603. Choice B, 0.6, is incorrect because it does not account for the decimal precision in the multiplication. Choice C, 0.603, is incorrect as it has the digits reversed when compared to the correct answer. Choice D, 0.06, is incorrect as it does not reflect the correct product of the two decimals being multiplied.

Correct Answer: A

Rationale: The correct answer is A, $33.59. To find out how much money she would have left, we need to calculate the total spending by adding the amounts spent at the groceries, dry cleaners, and pet store: $101.85 + $21.90 + $42.66 = $166.41. Subtract the total spending from the initial cash amount to determine the remaining cash: $200.00 - $166.41 = $33.59. Choice B, $29.59, is incorrect as it does not accurately reflect the correct calculation. Choices C and D, $25.59 and $21.59 respectively, are also incorrect as they do not consider the correct total spending amount and subtraction from the initial cash.

Correct Answer: C

Rationale: Calculate the increase in dosage: 100mg * 20% = 100mg * 0.20 = 20mg. Add the increase to the original dosage to find the new dosage: 100mg + 20mg = 120mg. Therefore, the new dosage is 120mg after a 20% increase from the original 100mg dosage. Choice A (80mg) is incorrect because it represents a decrease rather than an increase. Choice B (100mg) is the original dosage and does not account for the 20% increase. Choice D (140mg) is incorrect as it is the original dosage plus 40%, not the 20% increase specified.