Question 11
In the diagram below, $ABCD$ is a trapezium where $AD$ is parallel to $BC$. Points $P$, $A$ and $D$ lie on a straight line. Points $B$, $C$ and $Q$ also lie on a straight line. Line $PQ$ intersects $AB$, $BD$, $AC$ and $CD$ at $K$, $L$, $M$ and $N$ respectively, such that $PK=KL=LM=MN=NQ$. If $AD=20$ cm, what is the length, in cm, of $BC$?
