Correct Answer: B

Rationale: To solve for y, substitute y = 3 into the equation: 4(3) + 21 / 3 = 12 + 7 = 19. Therefore, the correct answer is 19. Choice A (7.7) is incorrect as it does not result from the substitution. Choice C (23/3) is incorrect as it does not match the calculated value. Choice D (11) is incorrect, as it is not the result of the provided equation.

Correct Answer: A

Rationale: The correct answer is A: 16.67%. When rolling a standard 6-sided die, each face has an equal probability of 1/6. Therefore, the probability of rolling a 5 specifically is 1/6, which is approximately 16.67% when converted to a percentage. Choices B, C, and D are incorrect because they do not reflect the correct probability of rolling a 5 on a standard die.

Correct Answer: A

Rationale: To subtract mixed numbers, find a common denominator. Converting 6 1/2 to 6 3/6 and 2 2/3 to 2 4/6, the calculation becomes 6 3/6 - 2 4/6 = 4 1/6. Therefore, the correct answer is A. Choice B (3 1/3) is incorrect as the correct result is not an improper fraction. Choice C (3 5/6) is incorrect as it does not represent the result of the subtraction. Choice D (4 1/3) is incorrect as it does not match the correct calculation.

Correct Answer: C

Rationale: To find out how many words a person can type in 20 minutes at a speed of 45 words per minute, you multiply the typing speed (45 words/minute) by the duration (20 minutes): 45 words/minute x 20 minutes = 900 words. Hence, the correct answer is 900 words. Choice A (800 words) is incorrect because it results from multiplying 45 words per minute by 18 minutes, not 20. Choice B (850 words) is incorrect as it is not the product of 45 words per minute and 20 minutes. Choice D (750 words) is incorrect because it is the outcome of multiplying 45 words per minute by 15 minutes, not 20.

Correct Answer: B

Rationale: To find the rate of calories burned per mile, divide the total calories burned by the total miles run: 2276 · 21.4 ≈ 106.4 calories per mile. This calculation gives the average number of calories burned for each mile of the marathon. Choice A, 107.5, is incorrect as it does not match the precise calculation result. Choices C and D are also incorrect as they are not the accurate rate of calories burned per mile based on the given data.