GEAR UP FOR LIFE

MATH MENTOR: Finding Percents

The word percent means “of 100.”  Basically, one percent is 1 part out of a whole with 100 parts.  Percents can be used to talk about the parts of a whole.  Any whole thing can be split into 100 equal parts.

One half of something is the same as 50% of something. One fourth of something is the same as 25% of something. One tenth of something is the same as 10% of something.

Another way of thinking about it is to say that

50% + 50% = 100% (the whole thing)

25% x 4 = 100%

10% x 10 = 100% (a whole thing)

Let’s say that 17 people out of 100 people vote for a new city park.  You could also say that 17% voted for a city park.

The percent sign (%) is used to indicate percents. Another way of indicating parts of a whole without the percent sign is to use decimals.

That means that .25 is the same as 25 parts out of a 100 or 25%.  Math is easier to do using .25 than 25%.  50% is the same as .50. 

What would 5% be?  If you think about money, it might help here.  5 cents are written .05.  That is exactly how 5 parts out of 100 are written as a decimal.  5% = .05.   Money may be helpful when trying to use decimals for percents.  (Notice the word cents in percents.)

Look at these problems.

100  x  .20 = 20.00*                                            

*You have a decimal point (a period) in front of two numbers in the problem.  Add a decimal point in front of the last two numbers.  That is, 20.00 or  20.

Multiplying by the decimal is the way to find percents for numbers other than 100, too.

For example, what is 10% of 20?  Do the math.  10% is the same as .10 so that when you multiply and put in your decimal point the answer is 2.

Try the following problems.

 1.        What is 25% of 36 employees?

  2.   What is 10% of 60 stores?

  3.     What is 50% of 90 citizens?

  4.    What is 20% of 75 cars?

  5.      What is 75% of 80 homes?

  ANSWER Find answer in reading. 1. 9 employees, 2. 6 stores, 3. 45 citizens, 4. 15 cars, 5, 60 homes

Here are two formulas (two accepted ways of solving problems).

If you have the total number and if you want to find a certain percent of that total number, do this:

Total:  50,000          Percent wanted:  25%

50000   X  .25  =  12,500

Answer:  25% of 50,000 is 12,500.

If you have the total number and a part of that number, and if you want to find what the part of the number is as a percent, do this:

Total:  50,000         Part of that total:  12,500

12,500   ÷   50,000  = .25     That means 25%

Answer:  12,500 of 50,000 is 25%.