Question

A four digit number is formed with the digits 1,3,4,5 without repetition. Find the chance that the number is divisible by 5:

• A. $\frac{3}{4}$
• B. $\frac{1}{4}$
• C. $\frac{9}{16}$
• D. $\frac{1}{16}$

Answer 1

The correct option is B $\frac{1}{4}$

Total possible number of 4 digits = 4! = 24
The number is divisible by 5 if unit digit itself is 5. Therefore we fix 5 at unit place and then remaining 3 places can be filled up in 3! ways.
Hence, the required probability = $\frac{3!}{4!}=\frac{6}{24}=\frac{1}{4}$