Weeds have taken over the paths (two squares). If mowed, they don't grow back, but unmowed weeds spread at speed $1$ along the road. What's the minimum speed of the mower to get rid of all the weeds? Roads are connected at each intersection and the mower must move on roads. 

[![enter image description here][1]][1] 


----------

I've edited the problem to reduce the number of squares from 9 to 2. But the dynamics of the optimal solution still seems eluding. The puzzle was initially asked [here](https://puzzling.stackexchange.com/questions/115893/the-mowers-challenge). 


  [1]: https://i.sstatic.net/03W8e.jpg