1st puzzle by Dr Harry Wiggins (Avoiding 2019)
Thabo writes down all the positive integers in order but he always avoids writing down the digits 2, 0, 1 and 9. So Thabo writes down 3, 4, 5, 6, 7, 8, 33, 34, 35, etcetera. Thus the 7th number he writes dow
n is 33. What is the 2019th number that Thabo would write down?
100-1000 = 216 numbers
1000-10000=1296 numbers
42+216+1296=1554 so we still need 465 more numbers
33333 is the 1555th number
34333 is the 1771st number
35333 is the 1987th number
35433 is the 2023rd number
Therefore the 2019th number is 35385