Quick - what's the answer? Don't know?
Here's a quick trick on how to figure out what different numbers are squared so you can fool people at parties into thinking you're a math genius with a calculator in your head or a nerd who has memorized what a bunch of numbers are squared.
If you know what one number is squared all it takes is a little addition or subtraction to figure out what the numbers around that number are when squared.
For example, let's start with an easy number like 20. 20 times 20 is 400. That's pretty simple because you only need to multiple 2 times 2 and add some zeros at the end. Same thing with 30 squared, 40 squared, etc. But what's 21 times 21? Instead of trying to multiple 21 times 21 in your head all you need to do is take 400 (20 squared) and then add 20 (the square root of 400) and 21 (the square root of 21 squared) and you get the answer: 441.
To find out what 19 squared is you just need to subtract 20 (the square root of 400) and 19 (the square root of 19 squared) from 400 to get 19 squared: 361.