## Thickness of mantle

1. The problem statement, all variables and given/known data

Given the density of the mantle to be 4700 kg/m^3, the density of the core to be 9700 kg/m^3, the radius of the planet to be 6050 km and the mean density to be 5240 kg/m^3, find the thickness of the mantle.

2. Relevant equations

I tried using the formula M = D * V and V = (4/3)(pie)(r^3) but there seems to be too much missing data.
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 Recognitions: Homework Help Science Advisor You have an equation linking volume (and so mass) of a sphere with radius. Now write the equation for the volume of the shell (ie mantle) which will depend on the thickness of the mantle ie, on the radius of the core. Then you have an equation something like overall average mass = mass of core (r_core) + mass mantle ( r_core )

 Quote by mgb_phys You have an equation linking volume (and so mass) of a sphere with radius. Now write the equation for the volume of the shell (ie mantle) which will depend on the thickness of the mantle ie, on the radius of the core. Then you have an equation something like overall average mass = mass of core (r_core) + mass mantle ( r_core )
So I end up having three equations...
1) Mtotal = Vtotal * Dtotal
2) Mcore = Vcore * Dcore
3) Mmantle = Vmantle * Dmantle

1) I have the V because I am given the radius and can also figure out the M because I am given the D.
2 & 3) I only have both D's and nothing else.

I also know that: 4) Mtotal = Mcore + Mmantle
Similarly, I know that: 5) Vtotal = Vcore + Vmantle

Equations (4) and (5) seems useless as I don't have information about the mass of either the mantle or the core and don't have information about the volume of the core or mantle.

Is there some way I can substitute equations... or am I even going about it the right way?

Recognitions:
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