A vessel contains oil (density `=0.8gm//cm^3`) over mercury (density `=13.6gm cm^3`). A homogeneous sphere floats with half its volume immersed in mercury and the other half in oil. The density of the material of the sphere in `gm//cm^3` is

Options

A. ` 3.3 `
B. ` 6.4 `
C. ` 7.2 `
D. ` 12.8`

Answer

C

Explanation

` (v)/(2) rho _(oil) g + (v)/(2) rho_(H g ) g = vd g `
` rArr (rho _(oil) + rho_(Hg))/(2) = d `
` (13.6 + 0.8 ) /(2 ) = d `
` rArr d = 7.2 `