Maximum height reached on earth is He=v22ge
90=v22ge
Maximum height reached on planet is
Hp=v22gp
90Hp=gpge..............(1)
Now acceleration due to gravity on earth is ge=GMe(Re)2,
acceleration due to gravity on planet is
gp=GMp(Rp)2=GMe10(Re3)2
gpge=910................(2)
From (1) and (2),
H=100 m