There are a number of ways of exploring around this area, don't
rush.
You might try 'trial and improvement' as one way to work towards a
square root of say 30, 50 or any other number.
Try this new method to find square roots for 30, 50, etc., then
check with a calculator to see that it's working out correctly.
Listen again to the audio as many times as you need. There's a lot
of calculation to follow.
When you are ready, think about the harder questions:
Why multiply by 2 and by 10?
And why look for an end digit that is also the digit you use to
multiply?