You may also like

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 Short
Challenge Level

Answer: 14

$2\times5$=$10$ and multiplying by $10$ adds a digit (a zero at the end)

$\begin{split}2^{18}\times5^{12}&=2^6\times2^{12}\times5^{12}\\
&=2^6\times\left(2^{12}\times5^{12}\right)\\
&=2^6\times\left(2\times5\right)^{12}\\
&=2^6\times10^{12}\\
&=2^6\text{ with 12 zeros afterwards}\\
&=\underbrace { 64}_{\text{2}}\underbrace{00...0}_{\text{12}}\end{split}$

So total $14$ zeros


You can find more short problems, arranged by curriculum topic, in our short problems collection.