A sweater that normally sells for $78 is marked 15% off. Which of the following estimates the sale price of the sweater?
- A. $12
- B. $66
- C. $22
- D. $69
Correct Answer: B
Rationale: To find the sale price after a 15% discount, you calculate 15% of $78, which is $11.70. Subtracting $11.70 from the original price gives $66.30. Since the price is typically rounded, the estimated sale price is $66. Choice A, $12, is too low and does not reflect a 15% discount off $78. Choice C, $22, and choice D, $69, are also incorrect as they do not accurately estimate the sale price after a 15% discount.
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Solve the equation 3(2x+5)=11x+5 for x. Which of the following is correct?
- A. 1
- B. 2
- C. -1
- D. -2
Correct Answer: B
Rationale: To solve the equation, distribute 3 to both terms inside the parentheses: 6x + 15 = 11x + 5. Then, move 11x to the left side by subtracting it from both sides: 6x - 11x = 5 - 15. Simplify to get -5x = -10. Divide by -5 to isolate x: x = 2. Therefore, the correct answer is x = 2. Choices A, C, and D are incorrect because they do not match the correct solution obtained by solving the equation step by step.
How many feet are in 9 yards?
- A. 45 ft
- B. 18 ft
- C. 36 ft
- D. 27 ft
Correct Answer: D
Rationale: To convert yards to feet, you need to know that 1 yard is equal to 3 feet. Therefore, to find out how many feet are in 9 yards, you multiply 9 by 3, which equals 27 feet. Choice A (45 ft) is incorrect as it miscalculates by multiplying 9 by 5 instead of 3. Choice B (18 ft) incorrectly multiplies 9 by 2. Choice C (36 ft) is incorrect as it doubles the answer of 18 feet, which is also an incorrect calculation.
What is the mathematical expression for 'Twelve less than thrice a number'?
- A. 3x-12
- B. 12-3x
- C. 3-12x
- D. 12x-3
Correct Answer: A
Rationale: The phrase 'thrice a number' translates to 3x, and 'twelve less than' means subtracting 12 from it. Therefore, the correct expression is 3x-12. Choice B, '12-3x', represents '12 less than a number thrice,' which is the opposite of the given phrase. Choice C, '3-12x', does not correctly interpret the phrase provided. Choice D, '12x-3', represents 'a number thrice less than twelve,' which is not the same as the original phrase.
What is 31% of 426?
- A. 425.69
- B. 132.06
- C. 13.7
- D. 0.07
Correct Answer: B
Rationale: To find 31% of 426, multiply 0.31 by 426. This gives 0.31 426 = 132.06. Therefore, choice B, 132.06, is the correct answer. Choice A, 425.69, is close to the original number but is not the correct answer for the percentage calculation. Choice C, 13.7, is not the correct result for 31% of 426. Choice D, 0.07, is significantly lower than the correct answer and does not represent 31% of 426.
What is a prime number?
- A. A number divisible by only 1 and itself
- B. A number divisible by 2 and 3
- C. A number divisible by any number
- D. A number with exactly three factors
Correct Answer: A
Rationale: The correct answer is A: 'A number divisible by only 1 and itself.' A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. This definition aligns with choice A. Choice B is incorrect because not all prime numbers are divisible by 2 and 3. Choice C is incorrect as prime numbers are not divisible by any number other than 1 and themselves. Choice D is incorrect because a prime number has exactly two factors, 1 and itself, not three factors.