## A community for students. Sign up today

Here's the question you clicked on:

## My15girl 2 years ago This is discrete functions. Can someone please help?? I can't figure out what I am doing wrong. I am supposed to get the indicated sum, but I keep doing something wrong. This is what series I have to work with x[15] for 0.3+0.003+0.00003+...... I know that a=0.3 and r=0.01 and n=15. so x[n] = a(r^n-1)/r-1 x[n] = 0.3((0.01)^15-1)/0.3-1 x[n] = 0.3((-1))/-7/10 but the outcome is 3/7. Is that the right outcome because the back of my text book says it's 10/33. And I don't understand what I am doing wrong. :/

• This Question is Closed
1. klimenkov

What is \(0.01^{15}\)?

2. My15girl

that would be the common ratio or "r" to the exponent number of terms or "n"

3. klimenkov

Can you calculate this?

4. My15girl

Yes, when I calculate it I get 1.E-30, then I subtract 1 and get -1

5. klimenkov

There is a mistake in the denominator. x[n] = 0.3((0.01)^15-1)/0.3-1

6. My15girl

oh

7. My15girl

wow, I am so clueless

8. klimenkov

Actually, there are two mistakes.

9. My15girl

Okay I see where I went wrong. Wow

10. My15girl

Thank you so much :)

#### Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy