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Numbers - General Aptitude

Q1:

2 + 22 + 23 + ... + 29 = ?

A 2044

B 1022

C 1056

D None of these

ANS:B - 1022

This is a G.P. in which a = 2, r = 22 = 2 and n = 9.
2
Sn = a(rn - 1) = 2 x (29 - 1) = 2 x (512 - 1)   = 2 x 511   = 1022.
(r - 1) (2 - 1)