# 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:

111 comments Page 1 of 12.
Shobha said:
1 week ago

I don't understand this logic - Then E = {TTT, TTH, THT, HTT, THH, HTH, HHT}.

As this question says event of getting at most two heads.

It should be these combinations- THH, HTH, HHT, HHH.

Please, someone, explain.

As this question says event of getting at most two heads.

It should be these combinations- THH, HTH, HHT, HHH.

Please, someone, explain.

Triveni said:
3 weeks ago

I can't Understand this. Anyone, please help me to get this.

Amit Verma said:
3 months ago

Here S = {TTT, TTH, THT, THH, HHH, HHT, HTH, HTT}

Let E = Even of getting at most two heads.

Then E = {HHH, HHT, HTH, THH},

P(E) = n(E)/n(S),

= 4/8 = 1/2.

Let E = Even of getting at most two heads.

Then E = {HHH, HHT, HTH, THH},

P(E) = n(E)/n(S),

= 4/8 = 1/2.

(9)

Tejeshwari said:
9 months ago

Thanks all for explaining it.

(2)

Zahid said:
1 year ago

How to find the events of coins quickly like TTT and HHT etc? explain me.

(1)

MUKESH MAHLI said:
2 years ago

At most mean- less than or less than equal to.

Am I right?

Am I right?

Dhivya said:
2 years ago

Thank you for explaining @Sundar.

Sumanth said:
3 years ago

It is 6/8=3/4.

(1)

Meena said:
3 years ago

The question is what is the probability of getting "at most" two heads?

Here, at most two heads mean Not more than two heads.

So, HHH is more than two heads. It is not counted in Event. Am I right?

Here, at most two heads mean Not more than two heads.

So, HHH is more than two heads. It is not counted in Event. Am I right?

(2)

Neeraja said:
3 years ago

@ Vivek Rai.

A coin is tossed 3 times. We have 8 possible outcomes. In those 8 possible outcomes, we should choose the outcomes in which we have 1 head, 2 heads or no heads (3tails). But according to you if you consider the only head side of the coin then how did you get 8 in the denominator?

So the answer is 7/8.

A coin is tossed 3 times. We have 8 possible outcomes. In those 8 possible outcomes, we should choose the outcomes in which we have 1 head, 2 heads or no heads (3tails). But according to you if you consider the only head side of the coin then how did you get 8 in the denominator?

So the answer is 7/8.

(3)

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