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When tossed, a certain coin has equal probability of landing on either [#permalink]
25 Dec 2007, 11:52

00:00

A

B

C

D

E

Difficulty:

45% (medium)

Question Stats:

50% (01:27) correct
50% (00:26) wrong based on 140 sessions

When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time?

Re: When tossed, a certain coin has equal probability of landing on either [#permalink]
25 Dec 2007, 12:06

1

This post received KUDOS

There are 8 possibilities for outcomes when flipping a fair coin 3 times.

2*2*2=2^3=8

of these 8 possibilities there are 2 with the coin landing on the same side each time. HHH and TTT.

so the probability is 2/8 or 1/4.

HHH -- works
HHT
HTH
HTT
THH
THT
TTH
TTT -- works

the standard .5*.5*.5=1/8 but that's just the probability of getting one SPECIFIC side 3 times in a row (ie probability of 3 heads). Since they don't care if it's 3 heads or 3 tails you have to multiply 1/8 by 2 (so now it's the probability of 3 heads OR 3 tails)

Re: When tossed, a certain coin has equal probability of landing on either [#permalink]
25 Dec 2007, 12:12

eschn3am wrote:

There are 8 possibilities for outcomes when flipping a fair coin 3 times.

2*2*2=2^3=8

of these 8 possibilities there are 2 with the coin landing on the same side each time. HHH and TTT.

so the probability is 2/8 or 1/4.

HHH -- works HHT HTH HTT THH THT TTH TTT -- works

the standard .5*.5*.5=1/8 but that's just the probability of getting one SPECIFIC side 3 times in a row (ie probability of 3 heads). Since they don't care if it's 3 heads or 3 tails you have to multiply 1/8 by 2 (so now it's the probability of 3 heads OR 3 tails)

thanks, i get that...just am not sure why the binomial distrib doesn't work for this problem...

When tossed, a certain coin has equal probability of landing [#permalink]
17 Aug 2010, 05:18

3

This post was BOOKMARKED

When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time?

Re: Some PS questions- Need explanation [#permalink]
17 Aug 2010, 06:24

1

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

udaymathapati wrote:

When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time?

A. 1/8 B. 1/4 C. 1/3 D. 3/8 E. 1/2

Winning scenario is if we'll have either three tails (TTT) or three heads (HHH): 1/2*1/2*1/2+1/2*1/2*1/2=1/4.

Re: Some PS questions- Need explanation [#permalink]
13 Jan 2014, 06:01

Bunuel wrote:

udaymathapati wrote:

Need help in explanation of following problems. Need to know how quickly we can solve such problems to save time.

4. When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time? A. 1/8 B.1/4 C.1/3 D.3/8 E.1/2

OA E

Winning scenario is if we'll have either three tails (TTT) or three heads (HHH): 1/2*1/2*1/2+1/2*1/2*1/2=1/4.

Answer: B.

Hi Bunuel,

if the question was "how high is the probability that you get only tails?" would it be answer B becaus 1/2*1/2*1/2 = 1/8?

Re: Some PS questions- Need explanation [#permalink]
13 Jan 2014, 06:22

Expert's post

unceldolan wrote:

Bunuel wrote:

udaymathapati wrote:

Need help in explanation of following problems. Need to know how quickly we can solve such problems to save time.

4. When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time? A. 1/8 B.1/4 C.1/3 D.3/8 E.1/2

OA E

Winning scenario is if we'll have either three tails (TTT) or three heads (HHH): 1/2*1/2*1/2+1/2*1/2*1/2=1/4.

Answer: B.

Hi Bunuel,

if the question was "how high is the probability that you get only tails?" would it be answer B becaus 1/2*1/2*1/2 = 1/8?

Re: When tossed, a certain coin has equal probability of landing [#permalink]
13 Feb 2015, 04:42

Hello from the GMAT Club BumpBot!

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Re: When tossed, a certain coin has equal probability of landing on either [#permalink]
27 Apr 2015, 19:03

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: When tossed, a certain coin has equal probability of landing on either [#permalink]
27 Apr 2015, 19:49

young_gun wrote:

eschn3am wrote:

There are 8 possibilities for outcomes when flipping a fair coin 3 times.

2*2*2=2^3=8

of these 8 possibilities there are 2 with the coin landing on the same side each time. HHH and TTT.

so the probability is 2/8 or 1/4.

HHH -- works HHT HTH HTT THH THT TTH TTT -- works

the standard .5*.5*.5=1/8 but that's just the probability of getting one SPECIFIC side 3 times in a row (ie probability of 3 heads). Since they don't care if it's 3 heads or 3 tails you have to multiply 1/8 by 2 (so now it's the probability of 3 heads OR 3 tails)

thanks, i get that...just am not sure why the binomial distrib doesn't work for this problem...

Complements of the GMAT Club Bot, I will attempt to answer your questions 8 years later.

Binomial distribution doesn't work here because you must take into account the probability of HHH or TTT. = 1/8 + 1/8 = 2/8 = 1/4

This means you will add the two probabilities. You're likely confusing this question with something along the lines of "If I flip a coin 3 times, what is the probability of getting all heads" = 1/8 .

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