First, we need to solve for the common ratio from
the data given by using the equation.
a(n) = a(1) r^(n-1)
12 = 6 r^(2-1)
r = 2
12288 = (6) 8^(n-1)
2048 = 8^(n-1)
n = 11
Then, we can find the sum by:
Sum of terms inside the brackets is 4095, i.e. 2^12 - 1.
So the required sum = 6 x 4095
= 24,570
