exponent question on gmatprep

[puniaball]

is there a quicker more efficient way to solve this problem without actually adding?

2+2+2^2+2^3+2^4+...+2^8

answer choices:

2^9
2^10
2^35
2^37

[truplayer256]

2+2+2^2+2^3+2^4+2^5+2^6+2^7+2^8

4=2^2

2(2^2)+2^3....+2^8

2(2^3)+2^4....+2^8

If you start to recognize the pattern in this question, it's clear that the answer is 2(2^8) or 2^9.

[PussInBoots]

Use simple logic: 256 + 128 + 64 + ... is obviously less than 1024, hence the answer is 2^9.

I'd memorize powers of 2.

[aspiregmat]

another possible approach...

its a GP series excluding the first 2.

Sn = a(r^n - 1)/r-1

here a = 2
r = 2
n = 8

ans = 2 +2(2^8 - 1) = 2^9