posted
I don't know. Maybe if I wasn't sick, I'd be able to figure this out myself. Maybe not.
I have a spreadsheet with budget numbers to be input programmatically. And I need to let the user input a number, and have it spread across 12 months, such that each month is X% higher than the previous month.
I can't figure out how to calculate it. As far as I can see, it's a series. If A is the total that's getting spread, and B is what gets multiplied on each month (1 + X%) and C is the amount that gets put in the first month, I have something like this:
A = C + CB + CB^2 + Cy^B + ... +CB^11
And I have A and B, so it should be possible to solve for C. But I can't do it. O Brains of Hatrack, can you help me?
Posts: 12266 | Registered: Jul 2005
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Take the reciprocal (the only step I'm questionable about - seems if we know C and A are non-zero, should be ok):
C = A/(1 + B + B^2...)
Or you could factor out C and divide by (1 + B + B^2...) on both sides. That quantity can't be zero unless X = -100%, which I doubt.
Posts: 13680 | Registered: Mar 2002
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