What is the probability of getting at least 2 heads in a row

Question

What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

A. 1/8
B. 1/4
C. 3/8
D. 1/2
E. 5/8

Bunuel · Accepted Answer

The probability of  at least 2  heads  in a row  on three flips is the sum of the probabilities of the following three cases: HHT, THH and HHH.

Now, each case has the probability of  (\frac{1}{2})^3 , so  P=3*(\frac{1}{2})^3=\frac{3}{8} .

Hope it's clear.

kapac · Answer

If we don't read the question attentively, we will be very likely to make the wrong calculations. In my opinion:
1/2 X 1/2 X 1 (it doesen't matter) + 
+
1/2 (the probability of not getting a head after the first flip) X 1/2 (the probability of getting a head) X 1/2( the probability of getting a head again)
=
 1/4 + 1/8 = 3/8

kraizada84 · Answer

probability for HHT;

Total number of ways of arranging HHT keeping HH intact is 2!

probability = 2! * (1/2)^3

probability for HHH;

no of ways= 1

probability = (1/2)^3

hence required answer = 2! * (1/2)^3 + (1/2)^3 
 = 3* 1/8 = 3/8

Hope this helps...!!

kapac · Answer

Banuel's explanation is again the simpliest and the steadiest against mistakes.

JeffTargetTestPrep · Answer

We can assume the first two flips are heads (H) and the last flip is tails (T). Thus:

P(H-H-T) = 1/2 x 1/2 x 1/2 = ⅛

The only other way to get two heads in a row would be flipping heads on the second and third flips.

P(T-H-H) = 1/2 x 1/2 x 1/2 = ⅛

Thus, the total probability of getting two heads in a row when we flip a coin three times is 1/8 + 1/8 = 2/8.

Next, we need to determine the probability of getting heads on all three flips.

P(H-H-H) = 1/2 x 1/2 x 1/2 = 1/8.

Thus, the probability of getting at least two heads in a row is 2/8 + 1/8 = 3/8.

Princ · Answer

total number case =2*2*2 =8
as listed below 
 HHH
HHT
THH 
HTH
TTH
THT
TTT
HTT

first 3 case have alteast 2 consecutive heads, so probability is 3/8

laborumplaceat · Answer

P(atleast 2 heads in a row) = P(2 heads in a row) + P(3 heads)

ways to get 2 heads in a row = HHT and THH
ways to get 3 heads in a row: HHH

So, final probability: 1/2^3*(3)
=3/8 (C)

What is the probability of getting at least 2 heads in a row

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What is the probability of getting at least 2 heads in a row

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