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Dolly Dolphin

Age 14 to 16 Short
Challenge Level

Dolly Dolphin swims at a constant speed. When she swims against a current of 2m/s, she travels at 6 m/s.

Dolly swims upstream in this current for 2 minutes, then turns round and swims back to her starting point. What is her average speed?

This problem is adapted from the World Mathematics Championships
You can find more short problems, arranged by curriculum topic, in our short problems collection.