The no. of waves made by an electron during its revolution in 5^th orbit is

We know that 

$\mathrm{mvr}=\frac{\mathrm{nh}}{2\mathrm{\pi }}$

Here the revolution is in 5th orbit so we get-

$\mathrm{mvr}=\frac{5\mathrm{h}}{2\mathrm{\pi }}$
or

$2\mathrm{\pi r}=\mathrm{mv}5\mathrm{h}$

or

$2\mathrm{\pi r}=5\mathrm{\lambda }$

Hence five times the wavelength of electron is equal to the circumference of 5th orbit. So the electron makes five waves around 5th orbit.