Square root of 800 equals (a) 2√20 (b) 20√2 (c) 40√2 (d) none of these

 Solution:

To find the square root of 800, we will express it in terms of its prime factors. 

It can be written as 800 = 2 × 2 × 2 × 2 × 2 × 5 × 5.

= 25×52

√800 = √(25×52)

= 5×22×√2

= 20√2

Hence option b is the answer.