Question

find a, and S, if a, = 1000, r = 10 and n=7​

Answer 1

Answer:

Correct question will be:-

ln a GP a= 1000,r=10 and n=7. Then find S ( sum of 7 terms)? [No need to calculate a as it is already given] .

Answer :-) As we know that

$a = 1000 \\ n = 7 \\ r = 10 \\S_n= \frac{a( {r}^{n } - 1) }{r - 1} \\ \implies S_7= \frac{1000( {10}^{7 } - 1) }{7 - 1} \\ = \frac{1000(10000000 - 1)}{6} \\ = \frac{1000 \times 9999999}{6} \\ = \frac{9999999000}{6} \\ = \frac{4999999500}{3} \\ = 16,666,66500\: \: \: \: \: \: \boxed{ \boxed{answer}}$