Gatebook Test

Question

Comments

A )

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How?

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When 1 is not mapped to 1 then it can map to any of the other 6 elements in 6 ways.

Let f(1)=2 then other 6 can form bijection in 6! Ways.

f(1)=3, again 6! Ways..

Like this 6*6! Ways..

Option A) 7!-6!=6!(7-1)=6*6!

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my mistake , thanks for correcting

Answer 1

This question can be seen as(just another perspective)

Consider there are 7 chairs and 7 boys in how many ways they can be sited such that the first boy should not be sited on the first  first chair.

so==> 7! (anyone one can sit any where)- 6! (first boy sits on the first chair )