Burning Down

One night two candles were lit. Can you work out how long each candle was originally?

Percentage Unchanged

If the base of a rectangle is increased by 10% and the area is unchanged, by what percentage is the width decreased by ?

Digit Sum

What is the sum of all the digits in all the integers from one to one million?

Big Product

Age 14 to 16 ShortChallenge Level

How many digits are in the product $2^{18}$ x $5^{12}?$

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