SAT Math Multiple Choice Question 152: Answer and Explanation
2. A website hopes to sign up 100,000 subscribers. So far, the website has signed up an average of 500 subscribers per day for d days. Which of the following represents the number of additional subscribers, W, the website must sign up to reach its goal?
- A. W = 500d
- B. W = 99,500d
- C. W = 100,000 - 500d
- D. W = 100,000 + 500d
Correct Answer: C
C Whenever there are variables in the question and in the answers, think Plugging In. Let d = 2. The number of subscribers the website has signed up so far can be calculated as 500(2) = 1,000. Therefore, the website needs to sign up 100,000 - 1,000 = 99,000 additional subscribers. Plug 2 in for w in the answers to see which answer equals the target number of 99,000. Choice (A) becomes W = 500(2) = 1,000. This doesn't match the target number, so eliminate (A). Choice (B) becomes W = 99,500(2) = 199,000. Eliminate (B). Choice (C) becomes W = 100,000 - 500(2) = 100,000 - 1,000 = 99,000. Keep (C), but check (D) just in case it also works. Choice (D) becomes W = 100,000 + 500(2) = 100,000 + 1,000 = 101,000. Eliminate (D). The correct answer is (C).