Question 5
Mr. Sun was traveling in an old bus that was moving at a constant speed on a road with kilometre markers, which indicate the distance in kilometres from the road’s start. Two examples of such kilometre markers are given below. A moment before falling asleep, he saw that the bus was passing a kilometre marker labelled with a two-digit number. After exactly one hour, Mr. Sun opened his eyes and saw the bus passing a kilometre marker labelled with a three-digit number, and he remembered that: its first digit was equal to the second digit of the number he saw before falling asleep, the second digit of the three-digit number was $0$, and the third digit of the three-digit number was equal to the first digit of the number he saw before falling asleep. Mr. Sun then slept for exactly two more hours before waking up, when he saw the bus passing a kilometre marker with a number that was almost the same as the second number, except that the second digit had been replaced by another digit. What was the speed, in km/h, of the bus?
