<em>yes it will be a rational number.</em>
square having area 400 sq units will have a length of 20 on each side by increasing the length of each side by 1 we get 21 then the area will be
21 ^ 2=441
Then we will have a rational number.
Square root of 4096 is 6.4 so the answer is 64 + 6.4 = 70.4.