# How do you calculate the distances of the perihelion and aphelion if you know that the period is 76 years and the semi major axis is 17.94 AU?

Kepler's 3rd law relates the period to the semi major axis as ${T}^{2} = {a}^{3}$. Now given the figures ${75}^{2}$ does equal ${17.94}^{3}$. In fact we only require one of these values as the other can be calculated from it.