It depends on what you mean by a four-digit number. Is 0033 a four-digit number? Is 0000? I can tell you that the largest four-digit number is 9999. If 0000 and all the four-digit numbers with leading zeros are four-digit numbers then all the numbers from 0000 to 9999 inclusive are four-digit numbers. If the four-digit numbers with leading zeros are not four-digit numbers then you need to subtract all the numbers from 0000 to 0999 inclusive.

Penny

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.