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Topic: Reach a Target Percentage
Replies: 3   Last Post: Aug 14, 2013 7:56 PM

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James Waldby

Posts: 356
Registered: 1/27/11
Re: Reach a Target Percentage
Posted: Aug 14, 2013 5:00 PM
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On Wed, 14 Aug 2013 20:17:54 +0000, Tom wrote:
> I wrote a companion program for Microsoft's Spider Solitaire on my Casio
> calculator. The program determines the "Win Rate" percentage based on how
> many current "Wins" and "Losses" in the game:

...
> For example, if there are currently 5260 wins and 145 losses, the "Win
> rate" is 97.3172988 percent. That seems to work fine.
>
> I've been using this program to determine how many total wins are
> necessary to reach a target percentage. To do this I have to re-run the
> program and incrementally enter "wins" until the target is calculated.
>
> What I would like to do is write a new program that would calculate,
> based on the current stats, how many more wins are necessary to reach a
> target percentage. For example, if I know the target is 98 percent and my
> wins are 5260 and losses are 145, how many total wins do I need to reach
> 98 percent?

...

Let t = target, eg t = 0.98 for 98%. Let w and l be the current number
of wins and losses, and d = number of additional wins needed to reach
the target percent. You want t = (w+d)/(w+l+d), or t*(w+l+d) = w+d,
or t*w + t*l - w = d - t*d, giving (t*(w+l) - w) / (1-t) = d.

--
jiw




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