A task which depends on members of the group noticing the needs of others and responding.

Do you know how to find the area of a triangle? You can count the squares. What happens if we turn the triangle on end? Press the button and see. Try counting the number of units in the triangle now. . . .

Make an eight by eight square, the layout is the same as a chessboard. You can print out and use the square below. What is the area of the square? Divide the square in the way shown by the red dashed. . . .

Points P, Q, R and S each divide the sides AB, BC, CD and DA respectively in the ratio of 2 : 1. Join the points. What is the area of the parallelogram PQRS in relation to the original rectangle?

You can move the 4 pieces of the jigsaw and fit them into both outlines. Explain what has happened to the missing one unit of area.

Can you find a general rule for finding the areas of equilateral triangles drawn on an isometric grid?

What are the areas of these triangles? What do you notice? Can you generalise to other "families" of triangles?

What happens to the area and volume of 2D and 3D shapes when you enlarge them?

Is it possible to remove ten unit cubes from a 3 by 3 by 3 cube made from 27 unit cubes so that the surface area of the remaining solid is the same as the surface area of the original 3 by 3 by 3. . . .

Seven small rectangular pictures have one inch wide frames. The frames are removed and the pictures are fitted together like a jigsaw to make a rectangle of length 12 inches. Find the dimensions of. . . .

Have a good look at these images. Can you describe what is happening? There are plenty more images like this on NRICH's Exploring Squares CD.

An activity for high-attaining learners which involves making a new cylinder from a cardboard tube.

Semicircles are drawn on the sides of a rectangle ABCD. A circle passing through points ABCD carves out four crescent-shaped regions. Prove that the sum of the areas of the four crescents is equal to. . . .

Prove that a triangle with sides of length 5, 5 and 6 has the same area as a triangle with sides of length 5, 5 and 8. Find other pairs of non-congruent isosceles triangles which have equal areas.

A tower of squares is built inside a right angled isosceles triangle. The largest square stands on the hypotenuse. What fraction of the area of the triangle is covered by the series of squares?

Explore this interactivity and see if you can work out what it does. Could you use it to estimate the area of a shape?

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

Are these statements always true, sometimes true or never true?

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

A simple visual exploration into halving and doubling.

Which is a better fit, a square peg in a round hole or a round peg in a square hole?

It is possible to dissect any square into smaller squares. What is the minimum number of squares a 13 by 13 square can be dissected into?

My local DIY shop calculates the price of its windows according to the area of glass and the length of frame used. Can you work out how they arrived at these prices?

This article for teachers gives some food for thought when teaching ideas about area.

Use the information on these cards to draw the shape that is being described.

What shape has Harry drawn on this clock face? Can you find its area? What is the largest number of square tiles that could cover this area?

In this game for two players, you throw two dice and find the product. How many shapes can you draw on the grid which have that area or perimeter?

Follow the instructions and you can take a rectangle, cut it into 4 pieces, discard two small triangles, put together the remaining two pieces and end up with a rectangle the same size. Try it!

What can you say about these shapes? This problem challenges you to create shapes with different areas and perimeters.

A hallway floor is tiled and each tile is one foot square. Given that the number of tiles around the perimeter is EXACTLY half the total number of tiles, find the possible dimensions of the hallway.

What is the largest 'ribbon square' you can make? And the smallest? How many different squares can you make altogether?

Polygons drawn on square dotty paper have dots on their perimeter (p) and often internal (i) ones as well. Find a relationship between p, i and the area of the polygons.

These practical challenges are all about making a 'tray' and covering it with paper.

Can you help the children find the two triangles which have the lengths of two sides numerically equal to their areas?

If you have only 40 metres of fencing available, what is the maximum area of land you can fence off?

Look at the mathematics that is all around us - this circular window is a wonderful example.

How can you change the area of a shape but keep its perimeter the same? How can you change the perimeter but keep the area the same?

What is the total area of the four outside triangles which are outlined in red in this arrangement of squares inside each other?

An investigation that gives you the opportunity to make and justify predictions.

A follow-up activity to Tiles in the Garden.

Grandpa was measuring a rug using yards, feet and inches. Can you help William to work out its area?

What is the largest number of circles we can fit into the frame without them overlapping? How do you know? What will happen if you try the other shapes?

Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?

What do these two triangles have in common? How are they related?

Use the interactivity to find all the different right-angled triangles you can make by just moving one corner of the starting triangle.

It's easy to work out the areas of most squares that we meet, but what if they were tilted?

How would you move the bands on the pegboard to alter these shapes?