You measure the width of your door to be 36 inches. The true width of the door is 75 inches. What is the relative error in your measurement?

Correct Answer: A

Rationale: The relative error is calculated using the formula: (|Measured Value - True Value| / True Value) * 100%. Substituting the values given, we have (|36 - 75| / 75) * 100% = (39 / 75) * 100% ≈ 0.52 * 100% = 0.52%. Therefore, the relative error in measurement is approximately 0.52%. Choice A is correct because it reflects this calculation. Choice B is incorrect as it represents a lower relative error than the actual value obtained. Choice C is incorrect as it overestimates the relative error. Choice D is incorrect as it underestimates the relative error.

Correct Answer: A

Rationale: To simplify the given expression, multiply the numerators together and the denominators together. 5/9 15/36 = (5 15) / (9 36) = 75 / 324. Now, simplify the resulting fraction by finding the greatest common divisor (GCD) of 75 and 324, which is 3. Divide both the numerator and denominator by 3 to get the simplified fraction: 75 · 3 / 324 · 3 = 25 / 108. Therefore, the simplified form of 5/9 15/36 is 25/108, which is equivalent to 5/36. Choice A, 5/36, is the correct answer. Choice B, 8/27, is incorrect as it does not match the simplified form of the expression. Choice C, 10/17, is unrelated and does not result from the given multiplication. Choice D, 15/27, does not correspond to the simplification of the given expression.

Correct Answer: C

Rationale: To calculate the circumference of a circle, use the formula 2πr, where r is the radius. In this case, with a radius of 3 inches, the estimated circumference would be 2 x π x 3 = 6π ≈ 18.85 inches. Therefore, the best estimate for the circumference of the frame is 18 inches (Choice C). Choice A (12 inches) is too small as it corresponds to the diameter rather than the circumference. Choice B (16 inches) and Choice D (24 inches) are also incorrect as they do not reflect the accurate calculation based on the given radius.

Correct Answer: A

Rationale: The student's score is calculated by adding the points earned for correct answers (x) and subtracting the points lost for incorrect answers (y/2). Therefore, the expression for the student's score on the exam is x - y/2. Option A is correct because it accurately represents this calculation. Option B (x - y) is incorrect as it does not account for the penalty of losing half a point for each incorrect answer. Option C (30 - (x + y)) is incorrect as it subtracts the total number of questions from the sum of correct and blank answers, which does not represent the scoring system. Option D (30 - x - y/2) is also incorrect as it incorrectly subtracts x from 30 and then deducts y divided by 2, which is not the correct scoring method for the exam.

Correct Answer: A

Rationale: When the sampling distribution of means is plotted, the distribution tends to be approximately normal, especially as the sample size increases. This phenomenon is described by the Central Limit Theorem, which states that the sampling distribution of the sample mean will be normally distributed regardless of the shape of the original population distribution as long as the sample size is sufficiently large. Choices B and C are incorrect because sampling distributions of means are not skewed. Choice D is incorrect because there is a predictable shape to the distribution, which is approximately normal.