Area - triangles, quadrilaterals, compound shapes

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 trapeziums each of equal area. How could he do this?

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

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?

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

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

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