Unit Conversion (mass, radius )

[Heat]

Homework Statement

In January 2006, astronomers reported the discovery of a planet comparable in size to the Earth orbiting another star and having a mass of about 5.5 times the Earth's mass. It is believed to consist of a mixture of rock and ice, similar to Neptune. Take mass Earth 5.97 x 10 ^24 and radius Earth 6.38x10^6.

If this planet has the same density as Neptune (1.76 g/cm^3), what is its radius expressed in kilometers?

What is its radius expressed as a multiple of Earth's radius?

Homework Equations

D=MV

The Attempt at a Solution

My attempt:

I got (5.97x10^24kg Earth's mass / 6380 km Earth's radius) x (.00176 kg mass of unknown planet mass / x the radius of the unknown planet)

= 1.068676422 x 10^-21

The answer does not seems right, I did convert each unit accordingly.

Please and thank you in advance.

 

[hage567]

Well for one thing, density is M/V, not M*V. I don't understand what you are doing. Where's your use of the density equation?

 

[Heat]

Nevermind, I solved it using the formula for finding the volume of sphere. In which it lead me to the final radius of 1.65 x 10 ^4 km.

Thank you anyways.


I just noticed the mistake of the D=M/V formula I stated before, can't believe I did that.