Question

A piece of iron weighs 44.5gf in air,39.5gf in water and 49.3gf in paraffin Calculate the density of Iron and the density of Paraffin

Answer 1

there is probably a mistake in teh given number for weight in paraffin liquid.  It is 40.3 gf rather than  49.3 gf

Relative density of  iron =  weight in air / (weight in air - weight in water)
             = 44.5 gf / (44.5 - 39.5) gf = 8.9
density of iron = 8.9 * 1000 kg /cubic meter = 8900 kg/ cub meter

relative density of  paraffin
    = (weight of iron piece in air - weight in paraffin) / (weight in air - weight in water)
   = (44.5 - 40.3 ) / ( 44.5 - 39.5)
   = 4.2 / 5 = 0.84

density of paraffin liquid =  840 kg/cubic meter

Answer 2

Relative density of  iron =  weight in air / (weight in air - weight in water)
also use
relative density of  paraffin
    = (weight of iron piece in air - weight in paraffin) / (weight in air - weight in water)