Find the average density of Venus if the radius is 6100 km And the acceleration of gravity is 8.8 m / s.

Free fall acceleration for Venus:
g = G * M / R ^ 2, where g = 8.8 m / s ^ 2, G is the gravitational constant (G = 6.674 * 10 ^ -11 m ^ 3 / (s ^ 2 * kg)), M – mass of Venus, R is the radius of Venus (R = 6100 km = 6.1 * 10 ^ 6 m).
M = ρ * V, where ρ is the average density of Venus, V is the volume of Venus (the volume for the ball is V = (4/3) * Π * R ^ 3).
Then: M = ρ * V = (4/3) * ρ * Π * R ^ 3.
g = G * M / R ^ 2 = G * (4/3) * ρ * Π * R ^ 3 / R ^ 2 = 4G * ρ * Π * R / 3.
ρ = 3g / (4G * Π * R) = 3 * 8.8 / (4 * 6.674 * 10 ^ -11 * 3.14 * 6.1 * 10 ^ 6) = 5163 kg / m ^ 3.
Answer. The average density of Venus is 5163 kg / m ^ 3.