You may also like

problem icon

Big Powers

Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.

problem icon

Rooted Via 10

How many of the numbers shown are greater than 10?

problem icon

Largest Expression

Which of these five algebraic expressions is largest, given $x$ is between 0 and 1?

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.