Correct Answer: A

Rationale: The correct inequality is 30c + 5p ≤ 100. This represents the combinations of ink cartridges (c) and printer paper (p) that Tom may purchase, ensuring the total cost is less than or equal to $100. Choice B is incorrect because the total cost should be less than or equal to $100, not equal to. Choices C and D are also incorrect as they indicate the total cost being greater than $100, which is not the case given Tom's budget limit.

Correct Answer: B

Rationale: The average length of a human eyelash is approximately one centimeter. A nanometer is too small to describe the length of an eyelash. A meter and a kilometer are much longer lengths and not suitable to describe the average human eyelash.

Correct Answer: C

Rationale: The range in the number of houses sold per year is calculated by subtracting the minimum number of houses sold from the maximum number of houses sold. In this case, the range is 42 (maximum) - 11 (minimum) = 31, not 29 as stated in the original rationale. Therefore, choice C (29) is incorrect. Choices A (20), B (25), and D (35) are also incorrect as they do not reflect the correct range of houses sold per year, which is 31.

Correct Answer: D

Rationale: To find the sale price after a 30% discount, you need to subtract 30% of the original price from the original price. 30% of $472 is $141.60. Subtracting this discount from the original price gives $472 - $141.60 = $330.40, which is the sale price Gordon paid. Choice A, $141.60, is incorrect as it represents only the discount amount, not the final sale price. Choices B and C are also incorrect as they do not account for the correct calculations of the discount and final sale price.

Correct Answer: C

Rationale: To find 1/6 of 500, multiply 500 by 1/6: (500)(1/6) = 500/6 = 83.33. Converting the fraction to a decimal gives 83.33. Rounding this to the nearest hundredth results in 83.33. Therefore, 83.33 milliliters of blood were used for further tests. Choice A is incorrect as it does not consider the decimal value of the fraction. Choice B is incorrect as it rounds to the tenths place, not the nearest hundredth. Choice D is incorrect as it rounds up unnecessarily, as the correct answer should be rounded to 83.33.