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Guys, I am a brainlet.
If you put $1000 in to a bank account at the start of each year and you get 5 % interest at the end of each year, how much do you have after 25 years? I know how to do this with a calculator or with a loop on a computer but I can't figure out how to do it with the formula for geometric or arithmetico-geoetric series.
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You mean this?:
[math]
1000 \cdot 1.05^{25} + 1000\cdot 1.05^{24} + ... + 1000 \cdot 1.05 \\
= 1000 \cdot \sum_{k=1}^{25}1.05^k \\
= 1000 \cdot \left(\frac{1.05^{26}-1}{1.05-1} - 1 \right)
[/math]
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>>9147858
Sum from k=1 to k=25 of q^k is (q^26-q)/(q-1), not (q^26-1)/(q-1)
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>>9147865
nvm I was trolling
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I got your back OP!
let bank balance be $
let interest rate be %
let time in years be T (no emoji support)
$$$=$*(1+%)^T
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Nvm guys. I got it by comparing the problem with the given notes and changing the use of the equation slightly. You wouldn't get it the way I did without the notes so don't bother trying.
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1.05^(n years) times original amount.
Thread posts: 7
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