[Blindmath] Seemingly basic math question involving probability

[Ramana Polavarapu]

As far as I can see, you are on the right track.  However, the probability
should be 1/2 but not 1/3.  We apply the multiplicative rule since we want
them to appear in the order specified.  Therefore, the right answer is 1/8.

Regards,

Ramana
 

-----Original Message-----
From: blindmath-bounces at nfbnet.org [mailto:blindmath-bounces at nfbnet.org] On
Behalf Of Matthew_2010
Sent: Thursday, October 01, 2009 4:26 AM
To: Blind Math list for those interested in mathematics
Subject: [Blindmath] Seemingly basic math question involving probability

Alright all, I'm embarrassed to ask but here goes.

Yesterday one of my kids asked me to help with a math problem he couldn't
work out and its been driving me a little crazy, so here I am. He was asked
to determine the probability of flipping a coin and getting heads on first
flip, heads on second flip, and tails on third flip. I'm thinking that
because these are independent events its a matter of multiplying 1/3 * 1/3 *
1/3. Therefore, the answer is that there is a 4% chance of flipping 3 times
and getting this pattern.

The part of the problem that's bugging me is the tails part. Shouldn't this
be a different probability since its the third flip and specified as tails? 
In other words, if the third flip was heads it wouldn't change the
probability at all since they would all be equal (1/3). What role does a
third tails flip play in the matter? (Hmm).

Matthew



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