A person can jump 1.5m on the earth. How high could the person jump on a planet having the twice the mass of the earth and twice the radius of the earth?

I believe you'd have to calculate the different planets info and use the formula you the problem used to find their height of the jump in order to find yours ...

F=mg=Gm1m2/r^2

g=Gm2/r^2

g=2Gm2 / (2r) ^2=2Gm2/4r^2=Gm2/2r^2

So since there is half times the gravity on this unknown planet that has twice earth's mass and twice it's radius, then the person can jump twice as high. 1.5*2 = 3m high