pls help me with this math problem??? pls elaborate and explain...Thankyou!?

(4/3)pi8^3 / [ (4/3)pi4^3 ] = 8

(1/8)160g = 20g

The formula for mass of the sphere m =Volume x density
=4/3 (pi) (r)^3 x density
m1= 160g, r1=8cm.
r2=4cm, m2=?
160=4/3 (pi) (8)^3x density-----(1)
m2=4/3 (pi) (4)^3x density-----(2)
now equation (2)/(1)
m2/160= (4)^3/(8)^3
m2=(4/8)^3 x 160
=160/8
=20 gm

Because the material is homogeneous, the mass ratio will be the same as the volume ratio

sphere volume = (4/3)πr³.
As (4/3)π cancels out, volume ratio of the two spheres = 4³/8³ = 2³ = 8
The mass of the smaller sphere is 160/8 = 20 g

mass=20g.... mass is related to volume (if the density won't object :p ) so its smthn lyk ---> V1/V2 = M1/M2 volume is in r^3 & others are similar in the fraction, so --- (r1)^3 /(r2)^3 = M1/M2 whch mns 4*4*4/8*8*8 = M/160 finlly M=20g