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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?

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  1. Meehan98
    • one year ago
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    The formula is: \[a _{n}= a _{1} r ^{n-r}\]

  2. Meehan98
    • one year ago
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    I keep getting $1968.30, but that's not right. The correct choices are: $2952.40 $51.10 $102.30 $984.10

  3. zepdrix
    • one year ago
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    Your solution that you came up with should be correct. Hmm thinking...

  4. zepdrix
    • one year ago
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    oh oh oh. No

  5. zepdrix
    • one year ago
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    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
    • one year ago
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    I have a sample problem that has the solution as well if that will help you.

  7. Meehan98
    • one year ago
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    I have a sample problem that has the solution as well if that will help you.

  8. zepdrix
    • one year ago
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    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
    • one year ago
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    Partial sum of a geometric series... mmm im trying to remember the formula >.< hehe

  10. zepdrix
    • one year ago
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    \[\large\rm \sum_{n=1}^{10} a_1 r^{n-1}=a_1\left(\frac{1-r^n}{1-r}\right)\]Does that formula look familiar? :)

  11. Meehan98
    • one year ago
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    I know the formula; I didn't think about the sum! Thank you!

  12. zepdrix
    • one year ago
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    If you only have ONE OPTION over 1968.30, that should help you narrow down your sum quite a bit ;) lol

  13. Meehan98
    • one year ago
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    Yes, so the sum would be: $2,952.40!

  14. zepdrix
    • one year ago
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    yayyy good job \c:/

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