Question

Find the least value for n which 1 +3+32+...3power n-1>1000​

Answer 1

we know Sn=a(r^n-2) upon r-1

Sum of the given G.P. is

Sn=1 (3^n-1) upon 3-1

Now according to question, we have

1 (3^n-1) upon 3-1>2000

3^n +1-1>4000

3^n +1>4001

3^7<4001<3^8

Therefore, n=7

your answer is 7