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Triangle
(Diagram not to scale.)
 
 
 
 
In the triangle $PQR$, the angle $QPR=40^{\circ}$ and the internal bisectors of the angles at $Q$ and $R$ meet at $S$, as shown. What is the size of angle $QSR$?

 

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

 

 


This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.