Scalene area

Can you find the area of this scalene triangle?
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative


The diagram shows a scalene triangle with side lengths 13 cm, 21 cm and 20 cm.

Image
Scalene area


From a point O inside the triangle, line segments can be drawn at right angles to each of the sides.


The lengths of these line segments are 9 cm, 3 cm and 3.6 cm, as shown in the diagram.

   


What is the area of the triangle?

This problem is adapted from the World Mathematics Championships