Number System Practice Test 2

Let three different one digit natural numbers be x, y and z.
Then, sum of all possible two digits numbers
= (10x + y) + (10y + x) + (10x + z) + (10z + x) + (10y + z) + (10z + y)
= 22x + 22y + 22z = 22 (x + y + z)
Hence, required number = 22.