Correct Answer: C

Rationale: To convert grams to milligrams, you need to multiply by 1000 since there are 1000 milligrams in a gram. So, to convert 63 grams to milligrams, you would calculate 63 * 1000 = 63,000 milligrams. Therefore, the correct answer is 63,000 mg. Choice A (630 mg) is incorrect as it would be the converted value if the original amount was 0.63 grams. Choice B (63 mg) is incorrect as it is the same value as the original grams. Choice D (63,000 mg) is incorrect as it is the same as the correct answer, but with a comma which is not standard when expressing numerical values.

Correct Answer: B

Rationale: To determine the percentage of income remaining after spending 15%, subtract the percentage spent from 100% (100% - 15% = 85%). Therefore, Mary has 85% of her income left, which aligns with answer choice B. Choice A (12%) is incorrect because it represents the remaining amount after spending 88% of her income. Choice C (75%) is incorrect as it does not account for the 15% already spent. Choice D (95%) is incorrect as it does not consider the amount spent by Mary.

Correct Answer: A

Rationale: The correct answer is A: 3000 meters. To convert kilometers to meters, you need to know that there are 1000 meters in 1 kilometer. Therefore, to find the number of meters in 3 kilometers, you multiply 3 by 1000, resulting in 3000 meters. Choice B, 2000 meters, is incorrect as it doesn't account for the correct conversion factor. Choice C, 3500 meters, and Choice D, 2500 meters, are also incorrect as they provide inaccurate conversions.

Correct Answer: A

Rationale: Let the width of the rectangle be x cm, and its length be 2x cm. The area of the rectangle is 2x * x = 2x², and the area of the square is 12² = 144 cm². Setting the areas equal gives 2x² = 144. Solving for x gives x = 6. Thus, the width is 6 cm, and the length is 12 cm. The perimeter is 2(6 + 12) = 36 cm. Therefore, the correct answer is 36 cm. Choice B, 46 cm, is incorrect because it does not match the calculated perimeter. Choices C and D are also incorrect as they do not reflect the correct calculation of the rectangle's perimeter.

Correct Answer: A

Rationale: The correct answer is A: 28. To find 28% of 100, you multiply 0.28 (the decimal equivalent of 28%) by 100. This calculation results in 28. Therefore, 28% of 100 is 28. Choice B, 20, is incorrect as it represents 20% of 100. Choice C, 25, is incorrect as it represents 25% of 100. Choice D, 30, is incorrect as it represents 30% of 100.