A $\textit{palindrome}$ is a number which reads the same forward as backward, for example 313 or 1001. Ignoring the colon, how many different palindromes are possible on a 12-hour digital clock displaying only the hours and minutes? (Notice a zero may not be inserted before a time with a single-digit hour value. Therefore, 01:10 may not be used.)
3 digits,
chose the first digit 9 choices 1,2,3,4,5,6,7,8,9
Chose the second 6 choices 0,1,2,3,4,5
chose the third, it has to be the same as the first so 1 choice
9*6*1=54 ways
Thanks for the correction EP.
4 digits
you can do this one yourself.