How many four digit palindromical numbres?

Answer 1

The first digit can be any one of nine (all except zero). For each of those . . .

The second digit can be any one of ten.

Total possibilities for the first two digits = 9 x 10 = 90.

Since the 4-digit number is a palindrome, the 3rd and 4th digits are determined

by the 1st and 2nd ones.

So the total number of 4-digit palindromes is the same as the number of possibilities

for the first 2 digits = 90 .