[tex]Ratio = \frac{radius of earth orbit}{radius of hydrogen atom}[/tex]
radius of earth orbit = 1.5 x 10^8 km = 1.5 x 10^11 m
radius of hydrogen atom = 0.37 A = 0.37 x 10^10 m
The trick is to make their units same. We changed it to metres.
Now, Ratio = [tex] \frac{1.5 \times 10^{11}}
{0.37 \times 10^{10} }[/tex]
Ratio = 40.5
