AP ICET 2015 Paper

Question : 147 of 200

Marks: +1, -0

If 8 persons sit in a row at random, then the probability that 3 particular persons among them sit together in a given specified order is

$3/28$
$1/8$
$1/56$
$1/7$

Validate

Solution:

Total no. of ways 8 persons can be seated in a row = 8!
Treating the 3 persons sitting together as a single entity, we now have 5 + 1 i.e.6 persons.
They can be arranged in 6! ways.
Since these 3 persons sit together in a specified order, no internal rearrangement is possible.
∴ Required probability

=6!/8!=1/{8×7}=1/56

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