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Re: Hard probability ! [#permalink]
21 Aug 2010, 12:54

All possible events = (1/2)^5= 1/32 all the favorable events HHHHH HHHTT THHHT TTHHH HHHHT THHHH that makes 6 favourable events Hence answer will 6/32 = 1/4 therefore B

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Re: Hard probability ! [#permalink]
23 Aug 2011, 16:51

Bunuel - U rock. +1 for you.

Cheers.!

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A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses?

A. 3/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32

Kaplan says the answer is 1/4. I think the answer is 3/16 because I have interpreted the qn as: What is the probability of getting atleast 3 consecutive heads -> 3 consecutive heads or 4 consecutive heads or 5 consecutive heads ?

Re: PS: Probability [#permalink]
24 Mar 2012, 13:29

Expert's post

shahlanuk wrote:

A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses?

A. 3/16 B. 1/4 C. 7/24 D. 5/16 E. 15/32

Kaplan says the answer is 1/4. I think the answer is 3/16 because I have interpreted the qn as: What is the probability of getting atleast 3 consecutive heads -> 3 consecutive heads or 4 consecutive heads or 5 consecutive heads ?

Merging similar topics.

Your interpretation is correct: at least 3 consecutive heads means 3, 4, or 5 consecutive heads, but the answer is still 1/4. Please check the solution provided above and ask if anything remains unclear.

Re: A fair coin is tossed 5 times. What is the probability of [#permalink]
15 Jul 2013, 06:03

1

This post received KUDOS

In this type of problems where repetition of values is allowed, the total number of possibilities is given by the formula n^r where n is 2 and has the values Heads and Tails. r is 5 and is equal to the number of tosses.

1. Total number of possibilities = 2^5 = 32 2. Instances of favorable outcomes:

(i) HHH** - Let us elaborate all the possibilities:

1. HHH HH 2. HHH HT 3. HHH TH 4. HHH TT

We have exhausted the possibilities.

(ii) We also have the following **HHH and the possibilities are: