Specific gravity of a mixture of antifreeze and water

[SnowOwl18]

----If 5.25 liter of antifreeze solution (specific gravity = 0.820) is added to 4.20 liter of water to make a 9.45 liter mixture, what is the specific gravity of the mixture?-----

I know that Specific gravity = density of substance/ density of water. The specific gravities of the antifreeze solution and the water are known...but I have no idea how to find the specific gravity of the mixture. Do I multiply the specific gravity by how many liters of the substance there is and then add the together? Thanks for any help.

 

[HallsofIvy]

Yes. Density of substance = mass over volume. You can think of specific gravity = density by taking your unit of mass to be the mass of one liter of water. Since the information you are given is specific gravity, that simplifies everything.

The 5.25 liter solution has mass= 5.25*0.820 mass units. The 4.20 liters of water has mass 4.20 mass units. Add those to find the mass of the mixture and then divide by its volume.

 

[SnowOwl18]

Thank you! Makes more sense now. :)