Meredith starts a saving fund for her son. She deposits $10 on his first birthday, $20 on his second, $30 on his third and so on....for 40 years (wow, is he still going to be living with her, too? Lol *ahem*....).
Use to determine how much she will have deposited in total (ignore interest at this point).
I don't understand how to plug this into the formula, example:
, which equals $320, but logic tells me that $10 + $20 +30, only equals $60.
What am I missing?
May 20th 2008, 06:11 AM
Meredith starts a saving fund for her son. She deposits $10 on his 1st birthday,
$20 on his 2nd, $30 on his 3rd, and so on for 40 years.
Use . . . . No!
That's not the formula . . . In fact, it's not any formula!
The sum of the first n terms of an arithmetic series is: . .
Now try it with: .
May 20th 2008, 06:20 AM
That first formula, could it be a typo and it should read n-1? That's the closest thing I can find in my book and it is the one on my pre-test sheet that they have given me....
BUT the formula you gave is RIGHT! It works on every term I have tried! THANK YOU!
May 20th 2008, 06:38 AM
And Soroban, can you help with part 2?
If Meredith's first deposit of $10 earns 5% interest, compounded monthly, what will the final deposit be?
Will it work if I tack on the end of that formula you gave me:
, where n=40?
May 20th 2008, 06:41 AM
Actually, n=480, correct? Because it will be 12 x 40?