Observations of jupiter and neptune?

Question

observations of jupiter and neptune show that they have orbital periods of 11.9 years and 164.8 years respectively. Using 5.2 AU as the distance of jupiter from the sun, what is the nearest AU distance of neptune from the sun?

Answer 1

Kepler's third law states that the square of the period of a planet is directly proportional to the cube of its distance from the Sun.

Therefore, (164.8)² = 27159.04

Take the cube root of this, and you get 30.059 AU.

Answer 2

kepler's 3rd law. plug in the numbers. what's the problem?