Question 46
The road between $A$ and $B$ is $15$ km long, firstly the road goes up, then it is flat, and lastly it goes down. It is known that every part is no less than $1$ km. The path made by a pedestrian takes exactly $3$ hours. What are the minimum and the maximum amount of time that is taken by the path in opposite direction, if it is known that the speed of pedestrian while going up is $4$ km per hour, while going straight is $5$ per hour and is $6$ per hour while going down?
(Rubliov Bogdan)
(Rubliov Bogdan)