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Triangle in a Triangle

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

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.
First inner triangle

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.