coin

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coin

by Xbond » Fri Aug 14, 2009 12:42 am
Hi there,

I would like to know the simplest process to resolve this PS. Explanation is requested

If a coin has an equal probability of landing heads up or tails up each time it is flipped, what is the probability that the coin will land heads up exactly twice in 3 consecutive flips?

a) 0.125
b) 0.25
c) 0.375
d) 0.50
e) 0.666
Source: — Problem Solving |

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Re: coin

by maihuna » Fri Aug 14, 2009 12:58 am
Xbond wrote: If a coin has an equal probability of landing heads up or tails up each time it is flipped, what is the probability that the coin will land heads up exactly twice in 3 consecutive flips?

a) 0.125
b) 0.25
c) 0.375
d) 0.50
e) 0.666
S = {TTT TTH THT THH HTT HTH HHT HHH}
H twice is in 3 ways i.e. THH HTH HHT so prob = 3/8 = 0.375
Charged up again to beat the beast :)

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by tohellandback » Fri Aug 14, 2009 1:46 am
IMO C
prob of heads=1/2
prob of tail=1/2

in 3 flips,
prob of 2 heads AND one tail
=1/2*1/2*1/2
=1/8
can be done in 3C2 ways
so 3*1/8=3/8=.375
The powers of two are bloody impolite!!

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by Xbond » Mon Aug 17, 2009 5:25 am
many thks guys

OA is C