If you want a decimal approximation, use the calculator; if you want it in reduced form, write it as a number times perfect squares.
First divide out 100's: 1 800 000 = 180 x 100 x 100
Divide up 180; it is divisible by 4 and by 9, leaving a 5.
1 800 000 = 5 x 4 x 9 x 100 x 100
√1 800 000 = √5 x √4 x √9 x √100 x √100
= √5 x 2 x 3 x 10 x 10
= 600√5
