Probability of coins

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vishubn: Legendary Member; Posts: 574; Joined: Sun Jun 01, 2008 8:48 am; Location: Bangalore; Thanked: 28 times

by vishubn » Mon Oct 20, 2008 10:39 am

I am sure it might be the easiest ... but i am no game for probablity

please comment....

A coin that is tossed will land heads or tails, and each outcome has equal probability. What is the
probability that the coin will land heads at least once on two tosses?

A. 1/4
B. 1/3
C. 1/2
D. 2/3
E. 3/4

OA E

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Source: Beat The GMAT — Problem Solving | Mon Oct 20, 2008 10:39 am

dmateer25: Community Manager; Posts: 1049; Joined: Sun Apr 06, 2008 5:15 pmFollowed by: 27 members; Location: Pittsburgh, PA; Thanked: 113 times; GMAT Score:710

by dmateer25 » Mon Oct 20, 2008 10:47 am

P(heads at least once) = 1 - P(Neither being heads)

P(Neither being heads) = (1/2)^2 = 1/4

P(heads at least once) = 1 - 1/4 = 3/4

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stop@800: Legendary Member; Posts: 871; Joined: Wed Aug 13, 2008 7:48 am; Thanked: 48 times

by stop@800 » Mon Oct 20, 2008 12:42 pm

HH
HT
TH
TT

so you need to select 3 out of 4
hence 3/4

www.interrogationpoint.com

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