Question

what is the sum of the first five terms of the geometric sequence in which a1=5 and r=1/5

Answer 1

If I remember correctly, the sum of a geometric sequence is:
\[\S _{n}=(a _{1}(1-r ^{n})/(1-r)\]
I'm not entirely sure, though.

Answer 2

express answer an improper fraction

Answer 3

Use \[s _{n} = a( 1-r^n)/(1-r)\]

so \[s _{n} = 5(1-(1/5)^5)/(1-1/5)\]

Answer 4

so 6.248?

Answer 5

and 6248/1000 in improper fraction form

Answer 6

Isn't that the formula for the nth term, rather than the one for the *sum* of the first n terms?

Answer 7

Yes