5. What is the total area in $\mathrm{cm}^{2}$ of the shaded region?
A 50
B 80
C 100
D 120
E 150
5. C The area of the whole rectangle is $200 \mathrm{~cm}^{2}$. Suppose the rectangle is cut in two by a vertical cut joining the midpoints of its longer edges and the right-hand half is then given a quarter turn about its centre to produce the arrangement as shown. It can then be seen that every grey region has a corresponding white region of the same shape and size. Hence, the total area of the grey regions is half the area of the rectangle and so is $100 \mathrm{~cm}^{2}$.