Question

If there are 6 periods in each working day of a school, in how many ways can one arrange 6 subjects such that each subject is allowed at least one period?

Answer 1

$6$ period $⟶$ $6$ subjects

Atleast $1$ period for each subjects

$\Rightarrow$$1$ period$⟶$ $1$ sibjects

There is no repetion of subjects

$\Rightarrow$ number of ways ${=}^6{P}_6$

$\Rightarrow \frac{6!}{0!}\Rightarrow 6!\Rightarrow 6\times 5\times 4\times 3\times 2\times 1\Rightarrow 720$

Therefore number of ways are $720$