Question

ABCD is a trapezium, P and Q are mid points of the diagonals AC and BD.
If AB=17cm and CD=9cm then the length of PQ is equal to

Answer 1

PQ = (17-9)/2 = 4

For a proof of this, see the last exercise at

http://jwilson.coe.uga.edu/MATH7200/Sect1.3.html