Copyright © University of Cambridge. All rights reserved.
'Triangle in a Triangle' printed from http://nrich.maths.org/
Take any triangle. Construct a point on each side so that the side length is divided in the ratio $1:2$
Now form a triangle by joining up these points.
Can you work out the fraction of the original triangle that is covered by this new inner triangle?
You may wish to try the follow-up problem Another Triangle in a Triangle.