9.2. Electronic clocks display time from 00.00.00 to 23.59.59. How much time during the day does the number on the display that reads the same from left to right and from right to left light up?
Answer: 96 seconds.

Solution. If the digits on the display are $a b . c d . m n$, then $a=0,1,2,0 \leq b \leq 9,0 \leq c \leq 5$, $0 \leq d \leq 9,0 \leq m \leq 5,0 \leq n \leq 9$. Therefore, if $a=n, b=m, c=d$, the symmetrical number on the display is uniquely determined by the digits $a, b$ and $c$, where $a=0,1,2,0 \leq b \leq 5,0 \leq c \leq 5$. In this case, if $a=0$ or 1, then $b$ and $c$ can be any digits from 0 to 5, the number of such number sets is $2 \cdot 6 \cdot 6=72$. If $a=2$, then $b=0,1,2,3 ; 0 \leq c \leq 5$ and the number of such sets is $4 \cdot 6=24$. In total, $72+24$ $=96$ sets of numbers, each of which is displayed for 1 second.