SAT Question of The Day 6th July 2013

3611,18, …

The first four terms of a sequence are shown above. Which of the following could be the formula that gives the nth term of this sequence for all positive integers n?

A.     2 times n

B.     (2 times n) + 1

C.     3 times n

D.     (n^2) + 1

E.     (n^2) + 2

One approach is plug in – n stands for the position of the term in the sequence.

If we plug in 1 to the formula instead of n we should obtain 3, when we plug in 2 we will get 6, 3 to give 11 and 4 to obtain 18.

Only n^2+2 delivers each time.

52% of 172,000 got it right.

P.S. in questions where plugging in seems to be the best option start from the last answer.

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