Boris Biker entered the Tour de Transylvania with an unusual bicycle whose back wheel is larger than the front. The radius of the back wheel is 40cm, and the radius of the front wheel is 30cm.
On the first stage of the race the smaller wheel made 120,000 revolutions. How many revolutions did the larger wheel make?
If you liked this problem, here is an NRICH task
that challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.