Estimating a Percent of Quantity
Lesson
Topic Index | Grade 6 Math | Intermediate Test Prep | StudyZone

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!
 

 
Topic Index | Grade 6 Math | Intermediate Test Prep | StudyZone

Created by Carol Carroll
Copyright 2001-06 Oswego City School District