How to find the square root of such math problems within seconds?

How to find the square root of this in seconds: 

You might be panicking after asked to find the square root of this math problem. 

But don't worry it's just a matter of seconds, I will tell you how: 

if you are asked a math problem of such as consecutive numbers and reverse added under square root, so the answer is the middle number which is four in the above problem. 

Let's do another one: 

the answer is simple it's 15. 

Now math is even more easy: 

The answer to this would be 55. 

Now can you say what's the answer to the first problem? 

Yes, you are right it's 200,000.