Probability
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Q.

A 5-digit number is formed by the digits 1,2,3,4, and 5 without repetition. What is the probability that the number formed is a multiple of 4?

 A.

1/2

 B.

1/3

 C.

1/4

 D.

1/5

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Solution:
Option(D) is correct

Total number of 5 digits number = 5! = 120.

Now to be multiply of 4, the last 2 digits of the number have to be divisible by 4. i.e. they must be 12, 24, 32 or 52. 

Corresponding to each of these ways there are 3! = 6, i.e. 6 ways of filling the remaining 3 places.

The required probability

\(=\dfrac{4\times 6}{120}\)

\(=\dfrac{1}{5}\)


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