In percentage problems, three quantities are involved. We call them the "Part" the "Whole" and the "Percent"

The three formulas for solving percent problems are:
Part = Percent x Whole
Whole = Part ÷ Percent
Percent = Part ÷ Whole

You can use a Percent Wheel to help you remember these formulas.

__Wheel.gif
To use a percent wheel, you place your finger over the value
you are trying to find.
The remaining segments of the percentage wheel will show you
the formula for finding that quantity.
____wheel.gif
If you need to find the percent, you place your finger over the %
symbol and you can see -
percent.JPG
W___wheel2.gif
If you need to find the whole, you place your finger over the W
and you can see -
whole.JPG
P___wheel.gif
If you need to find the part, you place your finger over the P
and you can see -
You should interpret this as % x W
part.JPG


Try an interactive activity here
This activity uses a very similar strategy, called a pyramid grid.


Then go to the next page and do some percentage activities


the three formulas for solving percent problems are:
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Source:
http://www.mathworks-training.com/PercentWheel.html