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 power, you will cover up the letter P.
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: <power
sample problems> 
The triangle: 
You can see that if you were trying to solve for Power
need to do know how much work was done in what amount of time, so if you
covered up the P, then the W(J) would be over the time (sec),
so you would divide the work done by the time you took to do it.
Similarly, if you wanted to solve for the amount of time the work took,
then the work(J) would be divided by the Power (Watts) you
applied since the work(J) is on the top. If you wanted to solve for
the work(J) it took to complete the task, then the Power (Watts)
would be located beside the time (sec), so you would multiply them
together.
(Units are included in italics in the
parenthesis)
