## Fanduekisses one year ago USE SUMMATION NOTATION TO WRITE THE SUM... pls help!

1. Fanduekisses

2. Fanduekisses

$\sum_{n=1}^{??} 10(3)^{n-1}$

3. Fanduekisses

@campbell_st

4. Fanduekisses

idk, I thought setting 7290 = 10(3)^n-1 would help but idk...

5. anonymous

looks good to me

6. anonymous

oh you need the upper limit right?

7. Fanduekisses

yes! ^_^

8. anonymous

$7290=10\times 3^{n-1}$ solve for $$n$$ via $279=3^{n-1}$ then just guess

9. anonymous

find a power of 3 that gives $$729$$

10. Fanduekisses

ohhhhh 9

11. anonymous

oops typo there $729=3^{n-1}$

12. anonymous

no i don't think so

13. anonymous

$$3^8=6561$$ too big try a smaller one

14. Fanduekisses

the bases have to be the same right?

15. anonymous

you are thinking too hard use a calculator $3^2=9\\ 3^3=27\\ 3^4=81\\ 3^5=...$ keep going until you get it, it will be soon

16. Fanduekisses

yeah 3^6

17. Fanduekisses

that's why the upper limit is 7

18. anonymous

ok so that makes your upper limit 7 i guess

19. Fanduekisses

thanks! :)