InterviewSolution
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InterviewSolution
| 1. |
The number of permutations of n different things, taken r at a time, in which P (r ≤ n − p) particular things will never occure is : (a) P (n − p, r) × P (n, n − p) (b) P (n, r) × P (n, p) (c) P (n, r) − P (n, p) (d) P (n − p, r) |
| Answer» <p style="text-align: justify;"><span style="font-family:Arial,Helvetica,sans-serif"><span style="color:#000000"><strong>Correct option (d) P (n − p, r)</strong></span></span></p><p style="text-align: justify;"><span style="font-family:Arial,Helvetica,sans-serif"><span style="color:#000000"><strong>Explanation:</strong></span></span></p><p style="text-align: justify;"><span style="font-family:Arial,Helvetica,sans-serif"><span style="color:#000000">Since p particular things out of n different things is never taken. So, we have to determine the number of ways in which r places can be filled with (n − p) distinct things. Clearly, the number of such arrangements is <sup>n − p </sup>P<sub>r</sub></span></span></p><p style="text-align: justify;"><span style="font-family:Arial,Helvetica,sans-serif"><span style="color:#000000">= P (n − p, r), where P (r ≤ n − p)</span></span></p> | |