h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Square Root of Five-digit Numbers

If you haven't got a book handy, then a commute is a good time for thinking abstract thoughts. One such abstract thought came to one Researcher who practises doing approximate square roots of five-digit numbers in his head.

Some people have way too much time on their hands...

***Self-depreciating humour. I salute you for being modest.***



But what really made me say,

"Whew. Holy Shit. I have the basic grasp on Mathematics, but this guy is way up in the ivory tower of Math."

WAS THE BELOW

***I have to say, "You are amusing."***



I invented this method while waiting for the number 9 bus in Southend. If you practise while you're on the tube you can get quite good at it, and then your friends will start calling you 'Rainman'. There is probably a better way of doing this, but I like this way because I thought of it by myself.
Remember the squares of the numbers from 1 (1) to 31 (961)

Think of a five-digit number: 65741

Take the first three digits: 657

What's the largest square number immediately below this? In this instance it's 625 (25 squared). Remember the square root of this number (ie.25) - the square root of 65741 is going to be 10 x this number

So the square root of 65741 is going to be 25n.nnn


>>okay... I believe you for no other reason but for the fact that I do not squareroot.

>>>alright... laugh at my ignorance.