SAT Math Multiple Choice Question 40: Answer and Explanation

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Question: 40

10. On Tuesday, a watchmaker made 4 more watches than he made during the previous day. If he made 16% more watches on Tuesday than on Monday, how many watches did he make on Tuesday?

  • A. 20
  • B. 21
  • C. 25
  • D. 29

Correct Answer: D

Explanation:

D Let's try out the answers and see which one works. Start with (B). If the watchmaker made 21 watches on Tuesday, then he must have made 17 watches on Monday. We know that he should have made 16% more watches on Tuesday than on Monday, so let's use the percent change formula to see if we get 16%: ≈ 23.5%, which is too big. Eliminate answer choice (B). We want the 4 watches to be a smaller percent of the total, so we need a bigger total. Try a bigger answer choice, like (D). If he made 29 watches on Tuesday, then he made 25 watches on Monday. Now the percent change is = 0.16 = 16%, which is exactly what we wanted. Therefore, (D) is your answer.

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