What is the square root of 2004 without a calculator?
I can see straight off without any working that it is just a little less then 45
Squaring numbers that end in 5 is really easy.
eg 75^2: 7*7+7=56 so the answer is 5625 works every time :))
So in your case
4^2+4=20
so 45^2=2025
44^2=(40+4)^2=1600+2*40*4+16=1936
So it is between 44 and 45, closer to 45 
Since sqrt(2004) is an irrational number so it cannot be written exactly in digits no matter how many digits that you use. :)
