Question 18
The diagram shows a rectangle made from three grey squares, each of area $25\,\mathrm{cm}^2$, inside a larger white rectangle. Two of the vertices of the grey rectangle touch the midpoints of the shorter sides of the white rectangle and the other two vertices of the grey rectangle touch the other two sides of the white rectangle. What is the area, in $\mathrm{cm}^2$, of the white rectangle? 