Calculate mass of planet whose density varies inversely proportional to radius.

this is extremely easy. simply assume a spherical shell at a distance x from the centre with incremental width of dx. now given that density= k/x.

so, dm= (k/x)*dv

but dv= 4pix^2dx

so dm= (k/x)*4pix^2dx= 4kpixdx

now simply integrate both sides

M= 4kpix^2/2 from 0 to R

or M= 2kpiR^2

kindly approve :)