Algebra Pre-Algebra and Basic Algebra Math Forum

 September 1st, 2019, 11:18 AM #1 Newbie   Joined: Sep 2019 From: Indiana Posts: 2 Thanks: 1 Very basic solution help. Hello it has been a while since I have engaged mathematics formally. I am trying to determine my odds of winning a contest. I had 1/300 chance of winning, and then received 1000 entries. This gave me 1/194 chance of winning. After receiving another 200 entries, I had a 1/181 chance of winning. Then, after another 420 entries, a 1/159 chance. Assuming the pool remains constant, how many entries must I submit to take my chances from 1/159 to 1/4 or 1/2 chance in winning. Thank you. September 1st, 2019, 02:44 PM #2 Senior Member   Joined: Jun 2019 From: USA Posts: 376 Thanks: 202 Assuming it's like a raffle... Let E be the original number of entries/tickets you had. Let T be the total number of entries in the pool. The odds of winning are E/T. So $\displaystyle \frac{E}{T} = \frac{1}{300}$ $\displaystyle \frac{E+1000}{T} = \frac{1}{194}$ $\displaystyle \frac{E+1200}{T} = \frac{1}{181}$ $\displaystyle \frac{E+1620}{T} = \frac{1}{159}$ You should be able to combine any two of these equations to solve for E and T. $\displaystyle \frac{E+1000}{T} - \frac{E}{T}=\frac{1000}{T} = \frac{1}{194}-\frac{1}{300}=\frac{53}{29100} \rightarrow T=\frac{29~100~100}{53}\approx 549~057 \rightarrow E\approx 1830$ Accounting for the odds being rounded, this works out for the other numbers. Therefore, you need roughly 137264 entries total for a 25.0 % chance of winning, or 274529 total for a 50.0 % chance of winning. Thanks from romsek September 2nd, 2019, 09:04 AM #3 Newbie   Joined: Sep 2019 From: Indiana Posts: 2 Thanks: 1 Thank you, Bones! Don't think I can accumulate that many, but I appreciate the work. Thanks from DarnItJimImAnEngineer Tags basic, solution Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post Aleoa Linear Algebra 1 April 21st, 2018 09:48 AM EyeMaze Linear Algebra 5 December 7th, 2014 08:57 AM rain Real Analysis 1 July 17th, 2013 01:28 PM maxgeo Algebra 1 July 26th, 2012 09:29 PM TreeTruffle Algebra 2 March 27th, 2010 02:22 AM

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