Question

Using each of the digits $1,2,3$ and $4$ only once, determine the smallest $4$-digit number divisible by $4$.

Answer 1

Finding the required number:

A number is divisible by $4$, when the last two digits of the number is divisible by $4$.

Therefore, from the given digits, $1,2,3$ and $4$ ,

The last two digits which can be formed to make a number is divisible by $4$ is either $12$ or $24$.

But, we have to form the smallest $4$ digit number, so our last two digits must be $24$.

Now, from the remaining digits, the first two digits of the number is either $13$ or $31$.

But the smallest first two digit is $13$.

Therefore, the smallest $4$ digit number which is divisible by $4$ is $1324$