A block of wood of density 0.70 gm/cm3 flaots in a mixture of water and alcohol of density 0.98 gm/cm3. What fraction of wood will be above the surface of mixture

According to Archimedes principle

weight of body immersed = weight of water displaced

so,

dgV = d'gV'

or

dV = d'V'

or

V/V' = d'/d

d = density of wood = 0.70 gm/c³

d' = density of water = 0.98 gm/c³

so, the fraction of volume under the surface would be

V/V' = 0.7/0.98 = 0.71 or 71%

or the fraction of volume of wood floating would be 0.29 or 29 %