Answer :
The orbital speed of the planet mercury can be calculated by the formula,
[tex]v=\frac{2\pi R}{T}[/tex]
Here, R is the orbital radius and T is the orbital time.
Given [tex]R=5.79\times10^{7} km[/tex] and [tex]T =88 days[/tex] (in second [tex]T= 88 \times 24 \times 60\times 60=88\times86400 s[/tex]
Substituting these values in above formula we get,
[tex]v=2\times\frac{22}{7} \times\frac{5.79\times10^{7} }{88\times86400}[/tex]
[tex]v=47.89 km/s\simeq 47.9 km/s[/tex]
Thus, the orbital velocity of the planet mercury is 47.9 km/s