## Meehan98 one year ago Help with Geometric Sequences and Series, please! David gave 10 cents to his daughter on her first birthday. He decided to give her triple the amount on each subsequent birthday. How much money would his daughter have received over a period of 10 years?

1. Meehan98

The formula is: $a _{n}= a _{1} r ^{n-r}$

2. Meehan98

I keep getting $1968.30, but that's not right. The correct choices are:$2952.40 $51.10$102.30 $984.10 3. zepdrix Your solution that you came up with should be correct. Hmm thinking... 4. zepdrix oh oh oh. No 5. zepdrix On the tenth birthday he gave her 1968.30, you are correct. But that is not the sum that he gave her over the period of all those birthdays. 6. Meehan98 I have a sample problem that has the solution as well if that will help you. 7. Meehan98 I have a sample problem that has the solution as well if that will help you. 8. zepdrix So this problem really is asking this:$\large\rm \sum_{n=1}^{10} a_1 r^{n-1}$They want you to add up all that money. 9. zepdrix Partial sum of a geometric series... mmm im trying to remember the formula >.< hehe 10. zepdrix $\large\rm \sum_{n=1}^{10} a_1 r^{n-1}=a_1\left(\frac{1-r^n}{1-r}\right)$Does that formula look familiar? :) 11. Meehan98 I know the formula; I didn't think about the sum! Thank you! 12. zepdrix If you only have ONE OPTION over 1968.30, that should help you narrow down your sum quite a bit ;) lol 13. Meehan98 Yes, so the sum would be:$2,952.40!

14. zepdrix

yayyy good job \c:/