Percent means part of a
hundred. So, let's look at what 25/100 means. It means the same as 25 out of every
100 and can be written as 25%.
In this lesson
we will learn how to estimate
percents. But first we will take a look at how to find the percent of a
number.
One way to
solve problems using percents is by writing an equation. 
Problem 
Find 10% of
$50 
Equation 
10% of $50 = n 

Write 10% as a decimal 

Remember "of"
means multiply 

0.1 x 50 = n 

n = 5 
Solution 
10% of $50 = $5.00 

Another
way to find the percent of a number is by writing a
proportion. 
Problem 
Find 20%
of $60 
Proportion 
First,
write the percent as a fraction.
20/100 

Next, write as a
proportion and solve.
20/100 = n/$60 

$60 x 20 = 100n 
Solution 
n = $60 x 20/100 or $12 

Let's
take a look at another example.
Find 5% of
200.
(Remember 5%=0.05)
Let n = the answer
0.05 (200) = n
10 = n


Now you're ready to move into
estimating percent of a number.
EXAMPLE : 
Estimate
Percent of a Number 


There
are 21 students in Mrs. Carroll's class, and
12 of them are girls.
About what percent of the class is girls?
Solution:
First, round off the numbers to numbers
that are easier to work with.
21 students ≈ 20 students
12 girls ≈ 10 girls
The "rounded" problem becomes 10 out of 20 students are
girls.
As a fraction that is 10/20
Reduce the fraction...1/2
1/2 = 50%
A good estimate of the percentage of
students in the
class who are girls is 50%. 


Remember: round
off to numbers that are easy to work with.

Let's Practice!
