Percent of Increase, Decrease, Discount
Topic Index | Algebra Index | Regents Exam Prep Center

There are many situations that involve increasing or decreasing an amount by a certain percent.  Check out the following examples:


You normally work at the mall over the spring break for $450.  This year the boss tells you that you will be receiving a 7% raise.  How much of an increase will you be receiving?  How much will you be earning in total this year?

Solution: Your raise is 7% of your old salary.

Let r = your raise
r = 7% 450
r = 0.07 450
  changing 7% to a decimal
r = 31.5 
Your raise will be $31.50.
Your total earnings will be $450 + $31.50
which equals $481.50.



Your dream CD player is on sale for 20% off the original price.  If the original price is $270, what is the sale price?

Solution: First, we will find the amount of the discount.

The discount = 20% of original price.
Let x =
the discount.
x = 20% 270
x = 0.20 270
x = 54
The discount is $54.

Now, the sale price will be $270 - $54
which equals $216 for the sale price.




The enrollment at a local elementary school had 560 students last year.  This year the enrollment has decreased by 48 students.  What is the percent of decrease to the nearest tenth of a percent?

The enrollment decrease =  the percent of decrease of 560.

Let x
= percent of decrease

Answer to nearest tenth of a percent:  8.6%