Question

a body weights 25g in air and 20g in water . what is the density of the material of the body ?

Answer 1

given , 
 weight in air ( W ) = 25g
 weight in water (W '  ) = 20 g
loss os weight in water ( W - W ' ) = 25 - 20g
                                                   = 5g
R.D. =  $\frac{W}{W - W ' }$
        = $\frac{25}{25-20}$ = 5

therefore , density = 5g/cc 

Answer 2

Weight of body in air (W) = 25 gms
Weight of body in water (W₂) = 20 gms
.·. Apparent loss in weight (W₁-W₂) = (25-20) gms
                                       = 5 gms.

Relative Density = W /W₁ - W₂
                         = 25/5
                         =5 (answer).