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Adrian measures the circumference of a circular picture frame with a radius of 3 inches. Which of the following is the best estimate for the circumference of the frame?
- A. 12 inches
- B. 16 inches
- C. 18 inches
- D. 24 inches
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.
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What is the value of b in this equation? 5b - 4 = 2b + 17
- A. 13
- B. 24
- C. 7
- D. 21
Correct Answer: C
Rationale: To find the value of b in the equation 5b - 4 = 2b + 17, you need to first simplify the equation. By subtracting 2b from both sides of the equation and adding 4 to both sides, you get 3b = 21. Then, dividing both sides of the equation by 3 gives you b = 7. Therefore, the value of b is 7, which corresponds to option C. Choice A (13) is incorrect as it does not match the correct calculation. Choice B (24) is incorrect as it is not the result of the correct algebraic manipulation. Choice D (21) is incorrect as it is not the value of b obtained after solving the equation step by step.
If Sarah reads at an average rate of 21 pages in four nights, how long will it take her to read 140 pages?
- A. 6 nights
- B. 26 nights
- C. 8 nights
- D. 27 nights
Correct Answer: D
Rationale: If Sarah reads 21 pages in four nights, she reads at a rate of 21 / 4 = 5.25 pages per night. To read 140 pages, she would need 140 / 5.25 = 26.67 nights. Since she cannot read a fraction of a night, it would take her 27 nights to read 140 pages, making option D the correct answer. Option A is incorrect as it does not accurately reflect the calculation. Option B is incorrect as it does not consider the fractional part of the calculation, resulting in an inaccurate answer. Option C is incorrect as it does not align with the correct calculation based on Sarah's reading rate.
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?
- A. 0.52%
- B. 0.01%
- C. 0.99%
- D. 0.10%
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.
In Jim's school, there are 3 girls for every 2 boys. There are 650 students in total. Using this information, how many students are girls?
- A. 260
- B. 130
- C. 65
- D. 390
Correct Answer: A
Rationale: To find the number of girls in Jim's school, we first establish the ratio of girls to boys as 3:2. This ratio implies that out of every 5 students (3 girls + 2 boys), 3 are girls and 2 are boys. Since there are a total of 650 students, we can divide them into 5 equal parts based on the ratio. Each part represents 650 divided by 5, which is 130. Therefore, there are 3 parts of girls in the school, totaling 3 multiplied by 130, which equals 390. Hence, there are 390 girls in Jim's school. Choice A, 260, is incorrect as it does not consider the correct ratio and calculation. Choice B, 130, is incorrect as it only represents one part of the total students, not the number of girls. Choice C, 65, is incorrect as it ignores the total number of students and the ratio provided.
Express the solution to the following problem in decimal form:
- A. 0.042
- B. 84%
- C. 0.84
- D. 0.42
Correct Answer: C
Rationale: The correct answer is C: 0.84. To convert a percentage to a decimal, you divide the percentage value by 100. In this case, 84% divided by 100 equals 0.84. Choice A, 0.042, is not the correct conversion of 84%. Choice B, 84%, is already in percentage form and needs to be converted to a decimal. Choice D, 0.42, is not the correct conversion of 84% either. Therefore, the correct decimal form of 84% is 0.84.