This question was previously asked in

SSC CGL Tier-II ( JSO ) 2018 Official Paper ( Held On : 14 Sept 2019 )

Option 3 : \(\dfrac{2}{5}\)

Cell

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10 Questions
10 Marks
7 Mins

**Concept:**

The formula of the probability of an event is:

P(A) = \(\rm \frac{Number of favourable outcomes}{Total number of favourable outcomes}\)

**Calculation:**

Total number of ways A, B, C, D and E can sit together = 5! = 120

Number of ways in which A and B sit together

lets stick A and B together and treat them as 1 unit let us name this unit as U now

we have UCDE

number of ways of arranging this is 4!

but number of ways of arranging U is 2!

so total number of ways are 4!*2! = 4 \(\times\) 3 \(\times\) 2 \(\times \) 1 \(\times\) 2 = 48

The probability that A and B sit next to each other is

= \(\rm \frac{48}{120}\)

= \(\dfrac{2}{5}\)

__Important Points__

Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur

Probability always lies from 0 to 1

The sum of probability of all possible outcomes is always 1