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Giant Holly Leaf

Find the perimeter and area of a holly leaf that will not lie flat (it has negative curvature with 'circles' having circumference greater than 2πr).


Given a square ABCD of sides 10 cm, and using the corners as centres, construct four quadrants with radius 10 cm each inside the square. The four arcs intersect at P, Q, R and S. Find the area enclosed by PQRS.

Get Cross

A white cross is placed symmetrically in a red disc with the central square of side length sqrt 2 and the arms of the cross of length 1 unit. What is the area of the disc still showing?


Age 14 to 16 Short
Challenge Level

Here is the solution from Christiane Eaves, Alicia Maltby, Kathy Lam, Rachael Evans andFiona Conroy (Y10) The Mount School,York:
The total surface area of the cube is $ 6r^2. $ The area shaded on one face is $ \frac{\pi r^2}{4}$ so the total shaded area is $ \frac{3\pi r^2}{4}.$

The fraction of the total surface area shaded is thus $\frac{3\pi r^2}{4}$ divided by $6r^2$ which is: $$\frac{3\pi r^2}{4} \times\frac{1}{6r^2}= \frac{\pi}{8}$$
You can find more short problems, arranged by curriculum topic, in our short problems collection.