Question Detail
Question
Find the sum of the first 22 terms of the geometric progression 2, 4, 8, ...
Correct Answer
Option A is the correct answer.
Detailed Explanation
a=2, r=2. S_n = a(r^n−1)/(r−1) = 2(2^22−1)/(2−1) = 2(4194304−1) = 2×4194303 = 8388606.
Hint
Use S_n = a(r^n−1)/(r−1) for r>1.