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In the star shown here the sum of the four numbers in any "line" is the same for each of the five "lines".

The five missing numbers are 9, 10, 11, 12, 13.

Which number is represented by R?










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.