A round table conference is to be held amongst 20 countries. If two particular delegates wish to sit…
A round table conference is to be held amongst 20 countries. If two particular delegates wish to sit together, then such arrangements can be done in ways.
$2 \times(18) !$
$\frac{19 !}{2 !}$
$18 !$
$19 ! \times 2 !$
Solution
We consider two particular delegates as single unit now 19 units can be arranged around a round table in 18! ways and the two delegates can be arranged mutually in 2 ! ways
Hence the required number of ways is $2 \times(18$ !)