# Moderate Probability Solved QuestionAptitude Discussion

 Q. One hundred identical coins each with probability '$p$' showing up heads and tossed If $0  ✖ A. 1/2 ✖ B. 49/101 ✖ C. 50/101 ✔ D. 51/101 Solution: Option(D) is correct Let$a$be the number of coins showing heads Then,$P(A=50)=P(A=51)\begin{align*} \Rightarrow ^{100}C_{50}\times P^{50}\times (1-P)^{50}\\ \Rightarrow ^{100}C_{51}\times P^{51}\times (1-P)^{49}\\ \Rightarrow ^{100}C_{50}\times P^{51}\times (1-P)^{50}=^{100}C_{51}\times P\\ \Rightarrow 51(1âˆ’P)=50P\\ \Rightarrow P = 51/101 \end{align*} ## (10) Comment(s) Aritra Das () Why^{100}C_{50}$and$^{100}C_{51}\$ and .... ? The coins are identical, meaning thereby that the only distinction between them is head or tails. As a result, it does not matter which 50 or 51 turn heads up.

Sushma Saroj
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yes that type of difficult questions shouldn't be asked in any kind of exams.

That type of questions is really tough

Sangeetha Mani
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I guess this question can be solved easily by using poisson distributiion

Shivanand
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Out of a hundred 'identical' coins, selecting one set of 50 coins is not different from selecting another set of 50 coins since they are all identical.

Parul
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No all u r are wrong.

These questions will make student think..

They would come to know their skills...

Sagar
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such questions makes students depressed and this the reason for unemployability...so its my humble, kind and genuine request not to post such questions to avoid any damage to students...

Hiren
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Such questions make students frustrated and that is the reason of students attempting suicide.

So, please don't post such tough questions?...

Parul
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And please Hiren can you tell me how due to dis ques can a person will attempt suicide...???

Ankit
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