Question 1011960
.
Similar problems were solved many times in few days.


The answer is: 17 + 17 = 34.


The info about 40 is excessive.


The idea of solution is that the points P, Q, R and S are vertices of a parallelogram. 
The sides of this parallelogram are mid-lines of triangles based on diagonals, 
and their dimensions are half measures of diagonals of the original quadrilateral.


See these lessons in this site:

<A HREF=http://www.algebra.com/algebra/homework/word/geometry/Midpoints-of-a-quadrilateral-are-vertices-of-the-parallelogram.lesson>Midpoints of a quadrilateral are vertices of the parallelogram</A>  and

<A HREF=http://www.algebra.com/algebra/homework/Triangles/The-line-segment-joining-the-midpoints-of-two-sides-of-a-triangle.lesson>The line segment joining the midpoints of two sides of a triangle</A>.