Geometric infinite series question

[Louise Johnson]

This question seemed way too easy so I am definately going to post it here as I have probably screwed it up somehow.

Question:
The first term of a geometric series is 2/5 and the sum of the infinite series is 4/5 and the common ratio is positive.
Determine:

#1 the common ratio
my answer I have 4/5=2/5 over 1-r
r=1/2

#2 The sum of the first five terms using a formula.
S5=2/5(1-1/2^5)/1-1/2
S5=4/5

Your help is really appreciated!
Thank you
Sincerly
Louise

 

[mark07]

#1 is correct.

Setup is correct in #2, but check your algebra... You should get 31/40.

 

[Louise Johnson]

Thanks Mark!
I was wondering about those questions !! I re-checked the second answer and I rounded up to 4/5 instead of just converting .775 to a fraction... I have a few issues with the basics which doesn't help things..
Thank you again that was a big help!
Louise