# Density

• Feb 1st 2010, 08:13 AM
andyboy179
Density
this is my question:

calculate the volume of a piece of wood which weighs 102g and has a density of 0.85g/cm^3?

would i do 0.85 x 102 =86.7 cm^3?
• Feb 1st 2010, 09:36 AM
TKHunny

By multiplying the two given values, your units are $\displaystyle \frac{gm^{2}}{cm^{3}}$. Does that look like volume to you?

If you divide the mass by the density, you get $\displaystyle \frac{gm}{\frac{gm}{cm^3}}\;=\;cm^{3}$. Does that look like volume?

Additionally, you should seek clarity from the definitions. What is the definition of density? Find it in your book. Mass/Volume? Something like that? Well, if you have Density = Mass/Volume and you are given Mass and Density, you are left with only a small algebra problem. Substitute and solve.

Note: Make sure you know the difference between Weight and Mass. They are NOT the same thing.
• Feb 1st 2010, 09:49 AM
andyboy179
would it be 1.25/4?
• Feb 1st 2010, 01:19 PM
TKHunny
Are you just making stuff up? Try using the values you were given.

Also, where are the units? Keep the units. Use the units. BE the units. They WILL save you.
• Feb 1st 2010, 10:36 PM
andyboy179
0.85/102= 0.0083 cm^3
• Feb 2nd 2010, 06:17 PM
TKHunny
Quote:

Originally Posted by andyboy179
calculate the volume of a piece of wood which weighs 102g and has a density of 0.85g/cm^3?

If you had included the units, rather than just guessing, you would have done this:

(0.85 g/cm^3)/(102 g) = (0.85/102)*(1/cm^3)

Is 1/cm^3 volume? No! cm^3 would be volume.

(102 g) / (0.85 g/cm^3) = ??