From the BBC:
Astronomers have found a previously unseen type of object circling a distant star. It could be the core of a gas world like Jupiter, offering an unprecedented glimpse inside one of these giant planets...
Its radius is about three-and-a-half times larger than Earth's but the planet is around 39 times more massive.
Woah! Why "but" and not "and"??
The formula for the volume of a sphere = 4/3 x pi x radius cubed.
Therefore a planet with three-and-a-half times the radius of earth has 43 times the volume.
If a planet has 43 times the volume of Earth and 39 times the mass, we can safely assume it has a pretty similar density to Earth.
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Screenshot attached just in case they correct the glaring mistake: