You may also like

problem icon

Areas and Ratios

What is the area of the quadrilateral APOQ? Working on the building blocks will give you some insights that may help you to work it out.

problem icon

Six Discs

Six circular discs are packed in different-shaped boxes so that the discs touch their neighbours and the sides of the box. Can you put the boxes in order according to the areas of their bases?

problem icon

Quadarc

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.

Griddy Region

Stage: 4 Short Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

$$\frac{11}{12} \; \text{square units}$$

solution

We want to find out how far the points $A$ and $B$ (the points on both the triangle and sqaure) are from $Y$. The triangle $OQT$ is $3$ units across by $2$ units down. The triangle $OPA$ is similar to $OQT$, and is half its size (since it is one unit down rather than two). So the point $A$ is $\frac{3}{2}$ units from $O$, so $\frac{3}{2}-1=\frac{1}{2}$ unit from $X$, so $1-\frac{1}{2}=\frac{1}{2}$ unit from $Y$

Similarly, the triangle $BST$ is $\frac{1}{3}$ the size of $OQT$, so the point $B$ is $\frac{2}{3}$ unit from $Z$, so $1-\frac{2}{3}=\frac{1}{3}$ unit from $Y$. So the triangle $AYB$ has area $$\frac{1}{2}\times \frac{1}{2}\times \frac{1}{3} \; \text{square units}= \frac{1}{12}\; \text{square units}$$ so the area of the overlap is $$1-\frac{1}{12}\; \text{square units}=\frac{11}{12}\; \text{square units}$$

This problem is taken from the UKMT Mathematical Challenges.
View the archive of all weekly problems grouped by curriculum topic

View the previous week's solution
View the current weekly problem