How far does the fly fly in the end?

[TSN79]

Two cyclists start cycling towards each other with an even speed of 10km/h. They start of 20km away from each other. At the same time a fly starts from one of them and flies to the other one, back to the first, and so on until they meet. How far has the fly flown in the end if it flew with a speed of 15km/h?

I'm thinking it has to be 15km, since the two guys will meet half way after 1 hour, and the fly flies 15km in one hour. Can someone confirm this?

 

[fargoth]

i confirm, you got it right

 

[Tide]

Just for fun, did anyone try the von Neumann method to solve the problem - with different speeds for the cyclists? :)

 

[TSN79]

Not yet, but as you said, it should be done - just for fun.

 

[d_leet]

Just for fun, did anyone try the von Neumann method to solve the problem - with different speeds for the cyclists? :)

That is exactly how my calc 2 teacher introduced us to series, starting with that question then telling the story about Von Neumann.