Aptitude - Probability - Discussion
Discussion Forum : Probability - General Questions (Q.No. 5)
5.
Three unbiased coins are tossed. What is the probability of getting at most two heads?
Answer: Option
Explanation:
Here S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH}
Let E = event of getting at most two heads.
Then E = {TTT, TTH, THT, HTT, THH, HTH, HHT}.
 P(E) = |
n(E) | = | 7 | . |
| n(S) | 8 |
Discussion:
121 comments Page 9 of 13.
Kishore said:
10 years ago
I think throwing 3 coins at a time is permutation not combination.
HTH = THH = HHT.
Reason is we did't mentioned the coins are different. So how can we say the first coin is Head second coin is Tail and third coin is Head.
If we throwing a single coin 3 times then we get combination like HHH, HHT, HTH, THH, TTT, THH, THT, TTH 8WAYS 1st throw second throw and third throw.
HTH = THH = HHT.
Reason is we did't mentioned the coins are different. So how can we say the first coin is Head second coin is Tail and third coin is Head.
If we throwing a single coin 3 times then we get combination like HHH, HHT, HTH, THH, TTT, THH, THT, TTH 8WAYS 1st throw second throw and third throw.
Manu said:
1 decade ago
Thanks very helpful.
Rajesh said:
1 decade ago
At most means 7/8.
At leat means 3/8.
At leat means 3/8.
Venkat said:
1 decade ago
Answer is 3/8 i.e. (C).
H T H.
H H T.
T H H.
H T H.
H H T.
T H H.
Joel said:
1 decade ago
At most 2 heads, so how did you include HHH?
Brian said:
1 decade ago
What is the probability of this question?
Riems said:
1 decade ago
Is there any direct method for calculating it? Because calculating n(e) may get confused in the exams time.
Ghanshyam said:
1 decade ago
How P(E) = n(E) upon n(S)= 7 by 8.
Sonali malviya said:
1 decade ago
Can anybody tell me why we have taken n(e) = 7?
Manan said:
1 decade ago
Can't it be like this:
Probability of all events = 3 heads, 2 heads, 1 head, 0 heads.
Hence n(s) = 4.
n(e) = 3.
Probability = 3/4.
Probability of all events = 3 heads, 2 heads, 1 head, 0 heads.
Hence n(s) = 4.
n(e) = 3.
Probability = 3/4.
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