##color(green)(=10sqrt2##

Square root of a number can be simplified by prime factorising the number.

Prime factorisation involves expressing a number as a product of prime numbers.
(##200## has ##2## and ##5## as its prime factors.)
So,
##sqrt(200) = sqrt(2*2*2*5*5)##
##sqrt200=sqrt(2^2 *2 *5^2)##
##=2*5sqrt2##
##color(green)(=10sqrt2##