Question

Find the sum of the given geometric progression.
1,2,4,8.......12 terms

Answer 1

1(

$1( {2}^{12 - 1} - 1) \div (2 - 1)$

$= {2}^{11 } - 1$

2047

Answer 2

here a=1 and d=2

sum of gp where r >1 ={ a(r^n-1)}/ r-1

so putting given values we get {1(2^12-1)}/2-1

that is 4095