Hi,

For a five digit number

_?_ ___ ___ ___ ___

the leftmost digit, ten thousands digit must be 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9. If the ?, the ten-thousands digit, is 0 then you don't have a five digit number, the number of digits is less than 5. Thus the ten- thousands digit is greater than 0 and hence the number is greater than any number with four digits.

Penny