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$PQR$ is a triangle and $S$ is a point on $QR$.

$QP=QR=9$ cm and $PR = PS =6$ cm.

What is the length of $SR$?

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.**View the archive of all weekly problems grouped by curriculum topic*