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InterviewSolution
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Let `S={1,2,...,20}` A subset `B` of S is said to be `"nice"`, if the sum of the elements of `B` is 203. Then the probability that a randomly chosen subset of `S` is `"nice"` is: (a) `7/(2^20)` (b) `5/(2^20)` (c) `4/(2^20)` (d) `6/(2^20)`A. `(6)/(2^(20))`B. `(4)/(2^(20))`C. `(7)/(2^(20))`D. `(5)/(2^(20))` |
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Answer» Correct Answer - D Number of subset of `S=2^(20)` Sum of elements in S is `1+2+......+20=(20(21))/2=210 ` `[therefore 1+2+......+n=(n(n+1))/2]` Clearly , the sum of elements of a sunset would be 203 , if we consider it as follows S -{7},S --·{1,G}S-{2,5},S-{3,4} S-{1,2,4) `therefore` Number of a favoueables cases =5 Hence , required probility `=5/(2^(20)` |
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