Lesson: Using proportions to convert fractions and percents

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Lesson Objective

We will use proportions to convert between percents and fractions.

Lesson Plan

Do Now: (5 minutes)
1) Write 25% as a fraction and decimal.

2) Write 0.4 as a fraction and a percent.

3) Write 3/8 as a decimal and a percent.

Direct Instruction: (20 minutes)
How are fractions, decimals, and percents the same?  Let's take a look at the work that we did on our do now problems.  (Go over method for each problem as a class).  Today we are going to continue to work with fractions and percents.  We are going to bring together our knowledge of converting fractions and percents and proportions.  Let's take a look at how that works.

What does percent mean? (Out of 100).  So what do we think we will need as part of our proportion?

Ex. Convert 4/15 to a percent.

 

Carefully go through the steps as a class with students writing the work in their notes.  When the problem is completed, review the steps together and add them to the notes.

To write a fraction as a percent:
1) Set up a proportion.  One ratio is the fraction.  The other ratio is a variable over 100.
2) Use cross multiplication to complete the proportion.

Remind students that part is across from part, whole is across from whole.

Ex. Convert 7/30 to a percent.


E. Convert 1 3/11 to a percent.
If I have one whole, what is that in percents?

Guided Practice: (10 minutes)
Ex. Convert 12/35 to a percent

Ex. Convert 8/45 to a percent

Ex. Convert  2 14/27 to a percent

Assessment: (10 minutes)
Converting fractions to percents work-out

 

Lesson Resources

fractions to percents work out   Assessment
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