Probability - coin toss - The Beat The GMAT Forum - Expert GMAT Help & MBA Admissions Advice

What is the probability of getting an identical result on three consecutive tosses of a coin?

a. 1/2
b. 1/4
c. 1/8
d. 1/16
e. 1/2 + 1/4

OA is B. Why not C?

The way I solved it: 3C3/2^3 = 1/8

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prindaroy: Master | Next Rank: 500 Posts; Posts: 113; Joined: Thu Jul 16, 2009 11:23 am; Thanked: 15 times; GMAT Score:730

by prindaroy » Sat Aug 08, 2009 6:46 pm

HHH = 1/2 * 1/2 * 1/2 = 1/8

TTT = 1/2 * 1/2 * 1/2 = 1/8

1/8 + 1/8 = 2/8 or 1/4

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tom4lax: Master | Next Rank: 500 Posts; Posts: 175; Joined: Mon Feb 09, 2009 3:57 pm; Thanked: 4 times

by tom4lax » Sun Aug 09, 2009 2:04 pm

First coin toss doesnt matter so probability is 1. Next 2 have to be identical to first, so 1/2 probability for each.

1*1/2*1/2 = 1/4

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