# Thread: Series Questions

1. ## Series Questions

Find the least value of n for which Sn>10000 for the sequence {3,6,12...}

and

A ball is dropped from a height of eight feet. The ball bounces to 80% of it's previous height of each bounce. How high (to the nearest tenth of a foot) does the ball bounce on the fifth bounce?

How do I solve these?

2. ## Re: Series Questions

Originally Posted by Diesal
Find the least value of n for which Sn>10000 for the sequence {3,6,12...}

and

A ball is dropped from a height of eight feet. The ball bounces to 80% of it's previous height of each bounce. How high (to the nearest tenth of a foot) does the ball bounce on the fifth bounce?

How do I solve these?
The first is a geometric series with a = 3 and r = 2. How would you evaluate the sum of the first n terms?

For the second, it's a geometric series with a = 1 and r = 0.8. How would you evaluate the sixth term? (the fifth bounce is the sixth term because after bounce 1 it's at 80% of the original height.)

3. ## Re: Series Questions

For the first one I have to find the series number that is greater than 10000?

So, 10000/3=2^n then find the log of both sides, and round to the next whole number?

And the second:
8(.8)^(6-1)?