Question

What is the least positive integer with which you have to multiply $243$ to get a perfect cube?

Answer 1

Let us factorise 243. We observe that
$243=3\times \left(81\right)=3\times 3\times 3\times 3\times 3.$
If we multiply $243$ by $3$, we see that
$243\times 3=3\times 3\times 3\times 3\times 3\times 3=9\times 9\times 9$,
and we get a perfect cube. The answer is therefore $3$.