$S_1, S_2, \ldots \ldots, S_{10}$ are the speakers in a conference. If $S_1$ addresses only after $S_2$, then the number of ways the speakers address is

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Aicharya · Accepted Answer

Since, $S_1$ speak after $S_2$, therefore two places can be chosen out of 10 place is ${ }^{10} C_2$ ways and rest of the 8 speakers can speak in 8 ! ways. $	herefore$ Required number of ways $={ }^{10} C_2 \cdot 8$ ! $ \begin{aligned} & =\frac{10 !}{2 ! 8 !} \cdot 8 ! \ & =\frac{10 !}{2 !} . \end{aligned} $

$S_1, S_2, \ldots \ldots, S_{10}$ are the speakers in a conference. If $S_1$ addresses only after $S_2$,…

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