At a school function the students stand so that the number of rows equals the number of students in each row. If there are 57 rows, how many students are on the ground altogether?

**Step 1**: factorise the number into primes.
**Step 2**: pair up identical factors.
**Step 3**: from each pair, take ONE factor — the product is the square root.

Example: $\sqrt{324}$. Factorise: $324=2^2\times 3^4=(2\times 3\times 3{)}^2$. So $\sqrt{324}=2\times 3\times 3=18$.

Example: $\sqrt{576}$. Factorise: $576=2^6\times 3^2=(2^3\times 3{)}^2$. So $\sqrt{576}=8\times 3=24$.

If any prime appears an odd number of times, the number isn't a perfect square — and you'd need to multiply (or divide) by that prime to make it one.