### Pebbles

Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?

### Square Areas

Can you work out the area of the inner square and give an explanation of how you did it?

### Kissing Triangles

Determine the total shaded area of the 'kissing triangles'.

# Nested Squares

##### Age 11 to 14 Short Challenge Level:

Splitting the diagram into one-inch squares
The largest square is 4 squares long, and the smallest square in the middle is 2 squares long.

Then, we can put the shaded pieces together to make whole square inches.

So there are 5 shaded squares, out of 16 squares in total.

So the proportion of the area which is shaded is $\frac5{16}$.

Finding the areas of the squares
The whole diagram is a 4 inch by 4 inch square, so has area 4$\times$4 = 16 square inches.

The shaded part is contained within a 3 by 3 square, so has area 3$\times$3 = 9 square inches.

There is a hole in the shaded part, which is a 2 by 2 square. So the area of the hole is 2$\times$2 = 4 square inches.

So the area of the shaded part is
9$-$4 = 5 square inches.

So the proportion of the area which is shaded is $\frac5{16}$.

You can find more short problems, arranged by curriculum topic, in our short problems collection.