ABCD is a square side 10. There are four points P1,P2,P3,P4 inside the square. Show that we can always construct line segments parallel to the sides of the square of total length 25 or less, so that each Pi is linked by the segments to both of the sides AB and CD. Show that for some points Pi it is not possible with a total length less than 25. combinatoricscombinatorial geometry