What is the difference between the sixth and the fifth terms of the sequence 2, 4, 7, … whose nth term is n+2^n-1?
(A) 2
(B) 3
(C) 6
(D) 16
(E) 17
ANS is E
I want to know, how the answer is 17.
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
sequence problem
This topic has expert replies
-
litteraround
- Junior | Next Rank: 30 Posts
- Posts: 21
- Joined: Tue Jun 10, 2008 1:27 pm
- Thanked: 3 times
hi,
you should post the question more clearly. The nth term is n+[2^(n-1)]. The way you posted it, it could be interpreted in more than one ways.
So, now the sixth term is: 6+2^(6-1) = 6 + 2^(5) = 6+32= 38.
And the fifth term is: 5+2^(5-1) = 5 +2^(4) = 5+16 = 21.
Therefore, the difference is 38-21 = 17. Voila!
you should post the question more clearly. The nth term is n+[2^(n-1)]. The way you posted it, it could be interpreted in more than one ways.
So, now the sixth term is: 6+2^(6-1) = 6 + 2^(5) = 6+32= 38.
And the fifth term is: 5+2^(5-1) = 5 +2^(4) = 5+16 = 21.
Therefore, the difference is 38-21 = 17. Voila!
