Hello cctest

Welcome to Math Help Forum!May I change your question a little, because this is what I think you mean. Calculate the total mass of a sphere of radius , if itsdensity(mass per unit volume) at a given point is given by where is the distance from the centre of the sphere. Is that it?

If so, then consider a thin spherical shell of radius , thickness . Its volume is its surface area multiplied by its thickness; i.e. . If its mass per unit volume is , then its mass is . To get the total mass, therefore, we integrate between and , to get

Mass

Obviously, you can't take this any further unless you know what is.

I hope that's what you were looking for.

Grandad