Question

find sq.root of 2304 in once and tens digits

Answer 1

The tens digit must be 4, 
since 40 x 40 = 1600 (too small) 
and 50 x 50 = 2500 (too large) 

I agree that the units digit must be 2 or 8. (since 2x2 = 4, and 8x8=64) 
42 x 42 is obviously too small 
48 x 48 is correct

so 48 is your answer