In making an alloy , a substance of specific gravity s1 and mass m1 is mixed with another substance of specific gravity s2 and mass m2 ; then the specific gravity of the alloy is
specific gravity of alloy=Density of alloyDensity of water=Mass of alloyVolume of alloy×densityof water=m1+m2(m1p1+m2p2)×pw=m1+m2m1p1pw+m2p2pw=m1+m2m1s1+m2s2[As specific gravity of substance=density of substancedensity of water]