Nope, because I don't have a copy, so I have no idea what he is doing - and I'm not about to spend money on anything to do with "interview question and answer" sets as they are all a waste of time and effort.
Interviews aren'#t run from a book, or a crib sheet - there is no standard list of questions an interviewer can ask, so there is no point in trying to memorise them with their answers because even in the unlikely event that one of them did come up, a follow up question would immediately reveal you lack of in-depth knowledge.
Much, much better to know your subject and get as much experience as possible (with your own projects if necessary) so that you actually know what the job entails instead ...
But square root approximation isn't difficult to understand: Methods of computing square roots - Wikipedia
] shows many methods, and Square root of ANY number instantly - shortcut math. - YouTube
] shows a very quick way to get a close approximation.