Correct Answer: D

Rationale: To find the value of x in the given ratio and proportion, we can set up the equation as 15:2000=x:200. Cross multiply to get x * 2000 = 15 * 200. Simplifying this gives x = 1. Therefore, the correct answer is D, which is 1. Choice A (7), Choice B (0), and Choice C (7,777) are incorrect as they do not match the correct calculation of x.

Correct Answer: A

Rationale: To find the total area covered by the stones, multiply the number of stones by the area each stone covers: 1,200 stones * 0.75 sq ft = 900 sq ft. Therefore, the stones will cover 900 sq ft, which is closest to 800 sq ft among the answer choices A, B, C, and D. The correct answer is A, 800 sq ft. Choices B, C, and D are incorrect as they do not result from the correct calculation of multiplying the number of stones by the area each stone covers.

Correct Answer: A

Rationale: If 3 bags of chips cost $4.50, then the cost per bag is $4.50/3 = $1.50. To buy five bags, John would need to pay 5 bags * $1.50 = $7.50. Therefore, it will cost John $7.50 to buy five bags of chips. The other choices are incorrect because they do not accurately calculate the total cost based on the given information.

Correct Answer: D

Rationale: To find the value of x, cross multiply in the ratio 18:x=10:300. This gives 18 * 300 = 10 * x. Solving for x, x = 540. Therefore, the correct answer is D. Choice A (16), Choice B (180), and Choice C (30) are incorrect because they do not satisfy the proportion equation 18:x=10:300 when cross multiplied.

Correct Answer: C

Rationale: To convert grams to milligrams, you need to multiply by 1,000 since there are 1,000 milligrams in a gram. Therefore, 7 grams is equal to 7,000 milligrams. Choice A (700 mg) is incorrect because it represents grams to milligrams incorrectly. Choice B (0.7 mg) is incorrect as it converts grams to milligrams erroneously by decimal placement. Choice D (0.07) is incorrect as it converts grams to milligrams inaccurately by misplacing the decimal point.