If there are five questions I have to answer, there are 5 alternatives to each question, and I need to get 3 right.
What are the odds I get 3 out of 5 right?
Thanks!
5 questions, get 3 right
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Hi,
Denominator: There are 5 ways to answer each of the 5 questions. Hence, the denominator is 5^5.
Numerator:
Number of ways of choosing the 3 questions in which we are going to be right = 5C3 = 10
Number of ways of answering the questions where we are going to be right = 1 *1 * 1
Number of ways of answering the questions where we are going to be wrong = 4C1 * 4C1 = 16.
Is the answer (10 * 16) / (5^5)? Pls clarify.
The assumption is that one HAS TO answer all the questions.
Thanks.
Denominator: There are 5 ways to answer each of the 5 questions. Hence, the denominator is 5^5.
Numerator:
Number of ways of choosing the 3 questions in which we are going to be right = 5C3 = 10
Number of ways of answering the questions where we are going to be right = 1 *1 * 1
Number of ways of answering the questions where we are going to be wrong = 4C1 * 4C1 = 16.
Is the answer (10 * 16) / (5^5)? Pls clarify.
The assumption is that one HAS TO answer all the questions.
Thanks.
Naveenan Ramachandran
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai
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i am bit confused...
but would be 5^5 wrong in this case as we may be able to select 2 options in one question....if it 1/5 in each case...
but would be 5^5 wrong in this case as we may be able to select 2 options in one question....if it 1/5 in each case...
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- Master | Next Rank: 500 Posts
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P(3 correct out of 5) = # of ways of choosing 3 questions * Prob of going right in those 3 questions * Prob of going wrong in the other 2 questionsandre.heggli wrote:I think it is the probability of getting P(3/5) + P(4/5) + P(5/5)
which would be 0.2^3 + 0.2^4 + 0.2^5
= 5C3 * (0.2 ^ 3) * (0.8^2) = 0.0512
Hope this helps.
Naveenan Ramachandran
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai