My Math Forum Probability of getting an even number of tails for x throws?

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 October 6th, 2013, 01:02 PM #1 Newbie   Joined: Oct 2013 Posts: 3 Thanks: 0 Probability of getting an even number of tails for x throws? Need help with the formula to calculate the probability for getting an even amount of tails after (0,1,2,...,491) coin flips. would be very thankfull for some help
 October 6th, 2013, 03:09 PM #2 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,923 Thanks: 1123 Math Focus: Elementary mathematics and beyond Re: Probability of getting an even number of tails for x thr If zero is considered even, the probability of getting an even number of tails on zero coin tosses is 1 and the probability of getting an even number of tails on every other number of tosses is 1/2.
 October 6th, 2013, 03:17 PM #3 Newbie   Joined: Oct 2013 Posts: 3 Thanks: 0 Re: Probability of getting an even number of tails for x thr well i know the probabilityis 1/2 but i think i need to do an binomial of it because i need to figure out the probability of getting a even number of tails in say 491 coin flips
 October 6th, 2013, 03:19 PM #4 Newbie   Joined: Oct 2013 Posts: 3 Thanks: 0 Re: Probability of getting an even number of tails for x thr only well motivated answers are accepted
 October 6th, 2013, 04:06 PM #5 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,923 Thanks: 1123 Math Focus: Elementary mathematics and beyond Re: Probability of getting an even number of tails for x thr There are 2^n possible outcomes, 2^(n - 1) of which have an even number of tails. 2^(n - 1)/2^n = 1/2.
 October 6th, 2013, 04:56 PM #6 Global Moderator   Joined: May 2007 Posts: 6,710 Thanks: 675 Re: Probability of getting an even number of tails for x thr You could use mathematical induction on the number of tosses if you want a formal proof.
October 6th, 2013, 05:23 PM   #7
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Re: Probability of getting an even number of tails for x thr

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 Originally Posted by Kuroniirp only well motivated answers are accepted

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