How many times is the radius of the 3rd shell of the hydrogen atom as compared to that of the radius of the first shell ?

How many times is the radius of the 3rd shell of the hydrogen atom as

1.	How many times is the radius of the 3rd shell of the hydrogen atom as compared to that of the radius of the first shell ?
Answer» Solution :`r_(N) = a_(0) n^(2)//Z`. For H, Z = 1 and for n = 3 `r_(3) = a_(0) xx 3^(2) = 9 a_(0)`