+230 In the diagram, two pairs of identical isosceles triangles are cut off of square $ABCD$, leaving rectangle $PQRS$. The total area cut off is $200 \text{ m}^2$. What is the length of $PR$, in meters?
+591 we can use pythagorean theorum to solve this problem, so PR^2 = PS^2+SR^2.
those two lengths are the hypotenuses of triagnles APS and SDR, so
PS^2+SR^2 = 2AP^2+2SD^2.
we also know that AP^2+SD^2=200, so AP^2+2SD^2=2(200)=400.
this means that PR^2=400, so PR=$\boxed{20}$
