Quote:
Two cities, Kensington, MD and Reston, VA are 30 km apart. From both of these cities, simultaneously, two hikers start their journeys towards each other. They are walking at a constant speed of 5 km/hour each. Simultaneously, a fly leaves the city of Kensington. It flies at the speed of 10 km/hour and passes the hiker from its city. When it reaches the Reston hiker, it turns around and flies back to the Kensington hiker. It keeps doing so until the hikers meet. If the fly lands on the shoulder of the Kensington hiker as he continues his journey to Reston at the moment the two hikers meet, how many kilometers has the fly flown?
I believe there is a flaw in the logic of the task.
When the fly meets the second hiker (from Reston), it flew 20km already. (\(2*10=20\)). It returns back to the first hiker (from Kensington). But the first hiker does not stop at the point of 10km, he moves forward with the speed of 5km/h. So does the second hiker. Thus, when the hikers meet, the fly cannot be in their meeting point, as its speed was 10km/h, not 5km/h, and it would be at the point of 10km, not 15km which is the meeting point for two hikers!