Percent Review

When converting decimals to percents, move the decimal point two places to the right.

For example: .15 = 15%

When trying to find a stated percent of a whole, simply turn your percent into a decimal by moving your decimal two places to the left and multiply.

For example: 50% of 30

50% should become .50

.50 times 30 = 15

When you know the percentage and the part you can use this information in the form of a proportion to solve for the missing piece.

For example:

The percent of change is the percent that a quantity changes from the original amount.

When the amount goes up we say that it increases.

When the amount goes down we say that it decreases.

When the new amount is larger than the original we need to find the percent of increase using this formula.
 $\frac{New\ amount\ -\ original\ amount}{original\ amount}$   

For example: 10 inches to 25 inches

Same idea as increase except you are subtracting the new amount from the original amount, like this:
 $\frac{Original\ amount\ -\ new\ amount}{original\ amount}$  

For example: 50 pounds to 35 pounds

When calculating markups and discounts, start by finding out what the question is asking. The process to find the percentage is the same as we previously reviewed.

Remember: When it is a markup you ADD it to the original amount.

When it is a discount you SUBTRACT it from the original amount.

Interest can be found by using the formula:

I=Prt or Interest = Principal x rate x time

For example: $600 at 5% for 2 years

600 x .05 x 2 = $60.00 for a new total of $660.00