TS ICET 23 May 2019 Shift 2 Paper

Question : 150 of 200

Marks: +1, -0

If four boys and five girls sit in a row at random, then the probability that all boys sit together is

Solution:

Treat 4 boys as one unit five girls and this unit of 4 boys can be arranged in

(5 + 1) = 6!

Ways.
Those 4 boys can be arranged internally in 4! ways
∴Total favourable cases

= 6!4!.

The required probability

=\;{6 ! 4 !}/{9 !}=\;{1}/{21}

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