What is the largest percentage error in the density of liquid water that can be made if the density is always assumed to be equal to 990 kg/m3 ? If 4 L of a liquid with density 1020 kg/m3 is mixed...

What is the largest percentage error in the density of liquid water that can be made if the density is always assumed to be equal to 990 kg/m3 ?

If 4 L of a liquid with density 1020 kg/m3 is mixed with 6 L of a liquid with density 940 kg/m3 , what is the density of the mixture?