Answer:
each of the planets moving  = 408.35 m/s
Explanation:
given data
mass = Â [tex]10^{24}[/tex] kg
distance between two planets = 2 × [tex]10^{8}[/tex] m
solution
if distance between two planet is 2 × [tex]10^{8}[/tex] m it mean it's diameter so
that radius will be 1 × [tex]10^{8}[/tex] m
and
F = [tex]\frac{G*m*m}{2r^2}[/tex] Â Â ................1
and
F = [tex]\frac{m*v^2}{r}[/tex] Â ..............2
so from equation 1 and 2 will be
[tex]\frac{G*m*m}{2r^2}[/tex] = Â [tex]\frac{m*v^2}{r}[/tex] Â
v = [tex]\sqrt{\frac{G*m}{4*r}}[/tex] Â Â ............2
put here value
v = [tex]\sqrt{\frac{6.67*10^{-11}*10^{24}}{4*10^8}[/tex] Â Â
v = 408.35 m/s