Question

A two-digit number is formed with the digits $2,5$ and $7$, where repetition of digits is not allowed. Find the probability that the number so formed is less than $57$

Answer 1

The possible outcomes when a two-digit number is formed with the digits $2,5$ and $7$ are {$25,27,52,57,72,75$}. Therefore, the number of possible outcomes when a two-digit number is formed with the digits $2,5$ and $7$ is $6$.

Now, the possible outcome of a number less than $57$ is {$25,27,52$}, which means the number of favourable outcome is $3$.

Therefore, probability $P$ of a number less than $57$ is:

$P=\frac{3}{6}=\frac{1}{2}$

Hence, the probability of a number less than $57$ is $\frac{1}{2}$.