Given,
Mass of the body, m=36 g
Density of the body, p=9 g/cm3
Density of water, σ=1 g/cm3
As we know, if two bodies are in equilibrium, it means both bodies have equal apparent weights. Therefore,
Apparent weight
=V(p−σ)g=mp(p−σ)g
m1p1(p1−σ)=m2p2(p2−σ)
369(9−1)=48p2(p2−1)
⇒p2=3