Question

Find the sum of the four-digit greatest number and the five-digit smallest number, each number having three different digits.

Answer 1

Calculate the sum

The four-digit greatest number having three different digits.: $9987$

the five-digit smallest number having three different digits.: $10002$

The sum of the four-digit greatest number and the five-digit smallest number, each number having three different digits:

$$\begin{gathered} =9987+10002 \\ =19989 \end{gathered}$$

Hence $19989$ is required solution.