Question

17. (a) In how many of the permutations of 12 things taken 3 at
a time will one particular thing (i) always occur
(ii) never occur?​

Answer 1

Answer:

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Step-by-step explanation:

MATHS

In how many of permutations of 10 things taken 4 at a time will (i) one thing always occurs, (ii) never occur?

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ANSWER

(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