Question Detail
Question
Sum of first 12 terms of GP 5, 15, 45, ...
Correct Answer
Option A is the correct answer.
Detailed Explanation
S_n = a(r^n−1)/(r−1)=5(3^12−1)/(3−1)=5(531441−1)/2=5×531440/2=5×265720=1,328,600.
Hint
Use S_n formula for GP.