Nishant Bhaiyya , haven't they asked for exactly two consequetive heads Because no where in the ques it is mentioned about at least two consequetive heads
what is the probability of getting two consecutive heads in five tosses of an unbiased coin
-
UP 0 DOWN 0 0 11
11 Answers
4(1/2)5?
This sum is very easy only because the probability of heads and tails is the same - 1/2 [4]
Subash there is 4 because the consecutive heads can appear in throws 1 & 2 or 2 & 3 or 3 & 4 or 4 & 5........
anirudh there is a mistake in your solution...
The question is not exactly 2 consecutive heads..
It should be 1- no consecutive heads.
= 1 - HTHTH - HTTHT - HTTTH - THTHT - THTTH - TTHTH - P(1 head)
= 1 - 6. (1/2)5 - 5. (1/2)5
= 1 - 11 (1/2)5
Check if I missed any cases.
@anirudh..
even there is a mistake in your cae of exactly 2 consecutive heads..
YOu have missed cases like
HHTHT, HHTTH, THHTH, HTHHT, THTHH, HTTHH
SO DO U MEAN TO HHHTH WILL NOT B COUNTED???
[12] [12] HMMMM.......... INTERESTING.......... FIR TO YEH ENGL KA QUESTN HO JAEGA!!! [3]
Well in any case the question will not be this vague in IIT..
So dont worry..
It is good that we have both the solutions.
But I think it does not mean "exactly" 2 consecutive heads.
In that case, as abhirup has pointed out the case HHTHH will be missed out!
HH*** 8 cases
THH** 4 cases
*THH* 4 cases
**THH 4 cases
Total no. of favourable cases 20
probability=20/32=5/8
bhiyaa u have missed the case with no heads ...i mean TTTTT
= 1 - HTHTH - HTTHT - HTTTH - THTHT - THTTH - TTHTH - TTTTT - P(1 head)
= 1 - 7. (1/2)5 - 5. (1/2)5
= 1 - 12 (1/2)5
=20/32
according to Nishant bhiyaa's method