You may also like

Kyle and his teacher disagree about his test score - who is right?

Tyneside Average Speed

Can you work out the average speed of the van?

Average Discovery

Find the missing number if the mean, median and mode are all the same.

Marathon Mission

Age 14 to 16 Short Challenge Level:

After a year's training, Minnie increased her average speed in the London Marathon by $25\%$.

By what percentage did her time decrease?

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.