Question

If blood has a density of 1.05 g/mL, how many liters of blood are donated if 672 g of blood are given?

Answer 1

convert the 672g to mL, then convert mL to L

Answer 2

Use the density information.
\[\color{green}{V = \dfrac{m}{\rho}}\]
That gives you the volume of blood, in mL. Only once you have done that, go ahead and convert to L.