Question

Question #424b7

Answer 1

I think you can just list them, then count. I make the total to be 6.

Explanation:

...and we'll disregard zero. For example, we will not claim that '01234' is a valid 5 digit number.

So you have:
12345
23456
34567
45678
56789

...and these are all the 5 digit numbers where the next digit is always greater by 1.

You can also write one 5 digit number where the next digit is greater by 2:

13579

...so, this makes 6 of them. Did I miss anything?

GOOD LUCK

UPDATE - fellow user EZasPI corrects me! His answer, as follows:
"I think there are quite a few missing, because it does not state that the next digit has to greater by 1. However, although I have several thoughts on this, I do not know how to calculate the actual number. For example: 12345, 12346. 12347, 12348, 12349, OR 13456,13457, 13458, 13459, 14567. 15678, 16789, 13579, and so on."

Of course, EZ is right!