A type of wood known as white pine has a density equal to 0.50 g/cm^3. What is the mass of a block of white pine that has the dimensions 5.0 cm by 10.0 cm by 200.0 cm?

Density = mass / volume.

So, mass = Density x volume

You have the information to get the volume in the problem:

5.0 cm x 10.0 cm x 200.0 cm = 10,000 cm^3

Now, find mass.

Mass = (.50 g/cm^3) (10,000 cm^3)

*cm^3 units cancel out*

= 5,000 g