Probability
Aptitude

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Q.

A five-digit number is formed by using digits 1, 2, 3, 4 and 5 without repetition. What is the probability that the number is divisible by 4?

 A.

1/5

 B.

5/6

 C.

4/5

 D.

None of these

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Solution:
Option(A) is correct

A number divisible by 4 formed using the digits 1, 2, 3, 4 and 5 has to have the last two digits 12 or 24 or 32 or 52.

In each of these cases, the five digits number can be formed using the remaining 3 digits in $3! = 6$ ways.

A number divisible by 4 can be formed in $6×4 = 24$ ways.

Total number that can be formed using the digits 1, 2, 3, 4 and 5 without repetition

$= 5! = 120$

Required probability,

$= 24/120$

$= \textbf{1/5}$


(1) Comment(s)


S Malik
 ()

any one please explain it with another method...