Question 10
In the diagram, $ABCD$ is a square. The common part of $ABCD$ and triangle $EFG$ is shaded. Its area is $\frac45$ of that of $EFG$ and $\frac12$ of that of $ABCD$. If the area of triangle $EFG$ is $40\text{ cm}^2$, what is the length of a side of $ABCD$, in cm?
