Correct Answer: B

Rationale: The correct answer is B: N/40. To find 40% of N, you multiply N by 0.4, so 0.4N is the correct representation. Choice B, N/40, is incorrect because dividing N by 40 does not give you 40% of N. Choice C, 2/5 N, is equivalent to 40% of N since 2/5 is the same as 40% when simplified. Choice D, 40N/100, is also correct since 40% can be represented as 40/100, which simplifies to 0.4, making 40N/100 another valid way to write 40% of N.

Correct Answer: A

Rationale: To calculate relative error, you use the formula: (|measured value - actual value| / actual value) * 100%. Substituting the values, we get (|36 - 35.75| / 35.75) * 100% = (0.25 / 35.75) * 100% = 0.7%. This means your measurement is off by 0.7% from the actual width of the door. Choice B, 0.01%, is too small as it doesn't reflect the actual difference. Choices C and D are significantly different from the calculated answer and do not represent the accurate relative error in the measurement.

Correct Answer: A

Rationale: When rounding a number to the nearest thousandth, you look at the digit in the ten-thousandths place to determine whether to round up or down the digit in the thousandths place. In this case, rounding 245.2678 to the nearest thousandth, the digit in the ten-thousandths place is 6, which is greater than or equal to 5, so you would round up the digit in the thousandths place. Therefore, the correct answer is the ten-thousandths place. Choices B, C, and D are incorrect because they do not directly influence the rounding of the thousandths place in this scenario.

Correct Answer: A

Rationale: To round 8.067 to the nearest tenth, you look at the digit in the hundredth place, which is 6. Since 6 is equal to or greater than 5, you round up the digit in the tenth place. Therefore, 8.067 rounded to the nearest tenth is 8.1. Choice B (8.1) is incorrect as it duplicates the correct answer. Choice C (8) is incorrect as it does not account for the decimal part. Choice D (8.11) is incorrect as it rounds the number to the nearest hundredth, not the nearest tenth.

Correct Answer: A

Rationale: The slope of the equation C = 50 + 75D is 75. This means that for each additional gigabyte used (represented by D), the cost (represented by C) increases by 75 dollars. Therefore, the correct interpretation of the slope is that it is 75 dollars per gigabyte. Choice B, 75 gigabytes per day, is incorrect as the slope does not represent the rate of data usage per day. Choice C, 50 dollars per day, is incorrect as it does not reflect the relationship between gigabytes used and the cost. Choice D, 50 dollars per gigabyte, is incorrect as it does not match the slope value of 75 in the equation.