The answer is 10 inches.
First thing to notice is the symmetry. Each bug will home in on its target at exactly the same speed, and each will approach the center at exactly the same speed. This means that the four bugs will always form a square.
Since they form a square, their travel paths will always be at right angles to one another. That means that at any given instant, Bug B's motion does not take it any closer or any further away from Bug A. Hence, Bug B's motion does not increase or decrease the distance Bug A must travel.
So Bug A must travel the 10 inches that was separating the two bugs at the start. This applies for the other bugs as well.
(Solution submitted by friedlinguini) |