In how many of the permutations of 10 different things taken 4 at a time, will one particulars things always occur?
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Answered by
1
Answer:
3024
I hope my answer will help you.
Step-by-step explanation:
(i) Total permutation of n different things taken r at a time when a particular item is always included in the arrangement is
r×
n−1
P
r−1
=4×
9
P
3
=4×9×8×7
=2016
(ii) Out of 10 different thing one thing never occur then 4 things will be occur out of 9 things
therefore
9
P
4
=
(9−4!)
9!
=9×8×7×6
=3024
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