Question 13
The given diagram shows how a square $ABCD$ with side length 40 may be dissected into six pieces by three straight cuts $AC$, $BD$ and $EF$, where $E$ and $F$ are the respective midpoints of $AB$ and $BC$. The pieces are then rearranged to form the given shape. What is the total area, in square centimetres, of the shaded part of the given shape?
