Read the following SAT test question, then click on a button to select your answer.

8, a, 14, b, 20, …

The first term of the sequence above is 8. Which of the following could be the formula for finding the nth term of this sequence for any positive integer n?

1. 2n + 6
2. 3n + 5
3. 5n + 3
4. 6n + 2
5. 6n + 5

Correct Answer: B

Here's Why:

You do not know the value of the 2nd term or the 4th term of the sequence, but you do know the values of the 1st, 3rd, and 5th terms. The correct formula must give 8 as the value of the 1st term, 14 as the value of the 3rd term, and 20 as the value of the 5th term. Choice E, 6n + 5, gives 11, not 8, as the value of the 1st term. Choice A, 2n + 6, gives 12, not 14, as the value of the 3rd term. Choice C, 5n + 3, gives 18, not 14, as the value of the 3rd term. Choice D, 6n + 2, gives 20, not 14, as the value of the 3rd term. This leaves choice B, 3n + 5, which gives the correct values for the 1st, 3rd, and 5th terms of the sequence.

Difficulty: Medium

Question Type: Standard Multiple Choice