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Age 11 to 14 Short Challenge Level:
The diagram shows a scalene triangle with side lengths 13 cm, 21 cm and 20 cm.
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
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.