The same as the number of two-digit numbers, since the last two digits
must the same as the first two, only reversed.
So I'll say there are 100 four-digit palindromes.
There are 90 palindromic numbers between 100 and 1000
90
9
There are 900000 of them.
10
There are 90 palindromic numbers between 100 and 1000
infinite
There are not just 13 non-palindromic numbers. Most numbers are non-palindromic.
90
9
There are 900000 of them.
1089
10
1089
Twenty.
Oh, dude, there are 90 three-digit palindromic numbers. You see, a three-digit palindrome has the form "ABA," where A and B can be any digit from 1 to 9. So, you just multiply the possibilities for A and B, which is 9 choices each, and voilà, you get 9 x 10 = 90. Easy peasy, lemon squeezy!
25001