These problems are not really
very hard to solve as long as you match the given numbers (usually using
their units) with the formula above. You can also use the triangle
method. The triangle is an easy way to figure out how to manipulate
the formula. In order to use it, look at the triangle. Put
your finger over the variable or letter you need to solve for. For
example, if you are looking for the density, you will cover up the letter
D. Now you do the mathematical function it shows. If the
letters are beside each other, you multiply. If one is on top of the
other, you divide. If you would like to check out some sample
problems, click on this link:
<density sample problems> 
The triangle: 
You
can see that if you were trying to solve for Density. Then the M (g,kg)
would be over the V (mL, L), so you would divide the mass by the volume. Similarly, if you wanted to solve
for Volume (mL, L) , then the mass (g, kg) would be divided by the density since the mass is
on the top. If you
wanted to solve for Mass (g, Kg) , then the Density (g/mL) would be located beside the Volume,
so you would multiply them together.
(Units are included in italics in the
parenthesis)
