Question

Find the sum of gemontrical sum3+ 6+12+.........1536

Answer 1

Answer:

3+6+12.......1536

Sn=1536

a=3

r=2

r>1

therefore Sn= a×rn-1 ÷r-1

1536= 3×2n-1÷2-1

1536÷3=2n-1

512÷2=n-1

256+1=n

n=257