The Question The Planet V has a year lasting 360 days. In the same star system is the Planet X. The Planet X has half the mass and triple the radius. A planet X year would be approximately _____ days The attempt at a solution Givens: Tv= 360days Tx= ? mv = mv mx = 1/2mv rv = rv rx = 3rv I derived a formula that incorporates time. From which v = sqrt ( GM/r ) since T = 2pir / v sub v into that formula and you get: T = sqrt (4 pi^2 r^ 3 / GM ) with that I had two sets of values, Vulcan and X: I plugged them into the formula and arranged for a common values such as Mv. Then I subbed Mv from one formula into another. This is what results: 8pi^23rv^3 / GTx^2 = 4pi^2rv^3/ GTv^2 through cancellations I ended up getting: Tx = sqrt ( (2)(3)^3(360)^2 ) which was that amount of days. Not sure if this method would be the correct way to go with this question or not.