What is a reasonable decimal answer for the sqrt of 200?

Answer 1

The sqrt of 200 is 14.14213562...

But a 'reasonable' answer would be 14.1

This is because the question gives three digits of precision -- called significant figures -- so it is reasonable to give three digits in the answer.

As another example, a reasonable decimal answer for the sqrt of 200.00 would be 14.142 (five figures in the question, five in the answer).