There are 10 of them. Here they are:
404, 414, 424, 434, 444, 454, 464, 474, 484, 494
There are 22 numbers between 400 and 600 that are divisible by nine.
400 of them.
300.
The answer is 400-100-1 = 299 (excluding both 100 and 400).
50
500
410
410
There are thirty-nine palindromic numbers between 10 and 400. They are 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, and 393.
There are 22 numbers between 400 and 600 that are divisible by nine.
400 of them.
300.
-200
The answer is 400-100-1 = 299 (excluding both 100 and 400).
50
59
The sum of the number of digits in all the numbers between 31 and 400 inclusive is 1041.