What if you knew that 25% of a number was equal to 24? How could you find that number? After completing this Concept, you'll be able to use the percent equation to solve problems like this one.
The percent equation is often used to solve problems. It goes like this:
Rate is the ratio that the percent represents (
Total is often called the base unit.
Part is the amount we are comparing with the base unit.
Find 25% of $80.
We are looking for the part. The total is $80. ‘of’ means multiply.
Express $90 as a percentage of $160.
This time we are looking for the rate. We are given the part ($90) and the total ($160). Using the rate equation, we get
$50 is 15% of what total sum?
This time we are looking for the total. We are given the part ($50) and the rate (15%, or 0.15). Using the rate equation, we get
Watch this video for help with the Examples above.
- A percent is simply a ratio with a base unit of 100—for example,
- The percent equation is
Rate×Total=Part, or R% of Total is Part.
- The percent change equation is
Percent change=final amount - original amountoriginal amount×100%.A positive percent change means the value increased, while a negative percent change means the value decreased.
$96 is 12% of what total sum?
This time we are looking for the total. We are given the part ($96) and the rate (12%, or 0.12). Using the rate equation, we get
Find the following.
- 30% of 90
- 27% of 19
- 16.7% of 199
- 11.5% of 10.01
- 0.003% of 1,217.46
- 250% of 67
- 34.5% of y
- 17.02% of y
- x% of 280
- a% of 0.332
Texas Instruments Resources
In the CK-12 Texas Instruments Algebra I FlexBook, there are graphing calculator activities designed to supplement the objectives for some of the lessons in this chapter. See http://www.ck12.org/flexr/chapter/9613.