There are **50** NRICH Mathematical resources connected to **Area - triangles, quadrilaterals, compound shapes**, you may find related items under Measuring and calculating with units.

We usually use squares to measure area, but what if we use triangles instead?

What are the possible areas of triangles drawn in a square?

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

Imagine different shaped vessels being filled. Can you work out what the graphs of the water level should look like?

Manufacturers need to minimise the amount of material used to make their product. What is the best cross-section for a gutter?

The diagonals of a trapezium divide it into four parts. Can you create a trapezium where three of those parts are equal in area?

Can you find the area of a parallelogram defined by two vectors?

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?

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

The area of a square inscribed in a circle with a unit radius is, satisfyingly, 2. What is the area of a regular hexagon inscribed in a circle with a unit radius?

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

Join the midpoints of a quadrilateral to get a new quadrilateral. What is special about it?

In this problem we are faced with an apparently easy area problem, but it has gone horribly wrong! What happened?

One side of a triangle is divided into segments of length a and b by the inscribed circle, with radius r. Prove that the area is: abr(a+b)/ab-r^2

Do you have enough information to work out the area of the shaded quadrilateral?

Start with a triangle. Can you cut it up to make a rectangle?

Can you work out the fraction of the original triangle that is covered by the green triangle?

Isometric Areas explored areas of parallelograms in triangular units. Here we explore areas of triangles...

Can you find the areas of the trapezia in this sequence?

We started drawing some quadrilaterals - can you complete them?

What's special about the area of quadrilaterals drawn in a square?

Can you make sense of the three methods to work out the area of the kite in the square?

Investigate the properties of quadrilaterals which can be drawn with a circle just touching each side and another circle just touching each vertex.

Can you draw the height-time chart as this complicated vessel fills with water?

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

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

Imagine an infinitely large sheet of square dotty paper on which you can draw triangles of any size you wish (providing each vertex is on a dot). What areas is it/is it not possible to draw?

Three fences of different lengths form three sides of an enclosure. What arrangement maximises the area?

Three squares are drawn on the sides of a triangle ABC. Their areas are respectively 18 000, 20 000 and 26 000 square centimetres. If the outer vertices of the squares are joined, three more. . . .

Draw any triangle PQR. Find points A, B and C, one on each side of the triangle, such that the area of triangle ABC is a given fraction of the area of triangle PQR.

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?

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?

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. . . .

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. . . .

Can you show that you can share a square pizza equally between two people by cutting it four times using vertical, horizontal and diagonal cuts through any point inside the square?

Take any rectangle ABCD such that AB > BC. The point P is on AB and Q is on CD. Show that there is exactly one position of P and Q such that APCQ is a rhombus.

Four rods, two of length a and two of length b, are linked to form a kite. The linkage is moveable so that the angles change. What is the maximum area of the kite?

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 trapezium is divided into four triangles by its diagonals. Can you work out the area of the trapezium?

The points P, Q, R and S are the midpoints of the edges of a non-convex quadrilateral.What do you notice about the quadrilateral PQRS and its area?

Straight lines are drawn from each corner of a square to the mid points of the opposite sides. Express the area of the octagon that is formed at the centre as a fraction of the area of the square.

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

A farmer has a field which is the shape of a trapezium as illustrated below. To increase his profits he wishes to grow two different crops. To do this he would like to divide the field into two. . . .

ABC and DEF are equilateral triangles of side 3 and 4 respectively. Construct an equilateral triangle whose area is the sum of the area of ABC and DEF.

Can you prove this formula for finding the area of a quadrilateral from its diagonals?

Three triangles ABC, CBD and ABD (where D is a point on AC) are all isosceles. Find all the angles. Prove that the ratio of AB to BC is equal to the golden ratio.

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?

Four rods are hinged at their ends to form a quadrilateral. How can you maximise its area?

The area of a regular pentagon looks about twice as a big as the pentangle star drawn within it. Is it?