Determine the total shaded area of the 'kissing triangles'.
You have a 12 by 9 foot carpet with an 8 by 1 foot hole exactly in the middle. Cut the carpet into two pieces to make a 10 by 10 foot square carpet.
It's easy to work out the areas of most squares that we meet, but what if they were tilted?
This article, written for teachers, discusses the merits of different kinds of resources: those which involve exploration and those which centre on calculation.
Can you work out the area of the inner square and give an explanation of how you did it?
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. . . .
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. . . .
A task which depends on members of the group noticing the needs of others and responding.
What fractions of the largest circle are the two shaded regions?
Investigate how this pattern of squares continues. You could measure lengths, areas and angles.
Which is a better fit, a square peg in a round hole or a round peg in a square hole?
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 circle with the radius of 2.2 centimetres is drawn touching the sides of a square. What area of the square is NOT covered by the circle?
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?
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 is the shape and dimensions of a box that will contain six cups and have as small a surface area as possible.
What is the total area of the four outside triangles which are outlined in red in this arrangement of squares inside each other?
This rectangle is cut into five pieces which fit exactly into a triangular outline and also into a square outline where the triangle, the rectangle and the square have equal areas.
This article for teachers gives some food for thought when teaching ideas about area.
A red square and a blue square overlap so that the corner of the red square rests on the centre of the blue square. Show that, whatever the orientation of the red square, it covers a quarter of the. . . .
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?
How would you move the bands on the pegboard to alter these shapes?
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.
Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?
Look at the mathematics that is all around us - this circular window is a wonderful example.
Explore one of these five pictures.
Derive a formula for finding the area of any kite.
You have pitched your tent (the red triangle) on an island. Can you move it to the position shown by the purple triangle making sure you obey the rules?
Bluey-green, white and transparent squares with a few odd bits of shapes around the perimeter. But, how many squares are there of each type in the complete circle? Study the picture and make. . . .
A follow-up activity to Tiles in the Garden.
Use the information on these cards to draw the shape that is being described.
I'm thinking of a rectangle with an area of 24. What could its perimeter be?
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?
How have "Warmsnug" arrived at the prices shown on their windows? Which window has been given an incorrect price?
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.
At the corner of the cube circular arcs are drawn and the area enclosed shaded. What fraction of the surface area of the cube is shaded? Try working out the answer without recourse to pencil and. . . .
What are the areas of these triangles? What do you notice? Can you generalise to other "families" of triangles?
Grandpa was measuring a rug using yards, feet and inches. Can you help William to work out its area?
Investigate the different ways of cutting a perfectly circular pie into equal pieces using exactly 3 cuts. The cuts have to be along chords of the circle (which might be diameters).
What happens to the area and volume of 2D and 3D shapes when you enlarge them?
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?
In how many ways can you halve a piece of A4 paper? How do you know they are halves?
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.
Can you help the children find the two triangles which have the lengths of two sides numerically equal to their areas?
Use the interactivity to find all the different right-angled triangles you can make by just moving one corner of the starting triangle.
Can you maximise the area available to a grazing goat?
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?
Imagine different shaped vessels being filled. Can you work out what the graphs of the water level should look like?
How many centimetres of rope will I need to make another mat just like the one I have here?