How to Convert Fractions

Preinstructional Planning

Objectives

Students will:

Indicate that fractions, decimals, and percentages are different ways to depict a part-to-whole relationship
Convert fractions to equivalent decimals and percentages to solve real-world problems

Materials

During Instruction

Set Up

Make class sets of the Conversions Rock Worksheet: Stardom: Just a Fraction Away printable and the Conversions Rock Bonus Worksheet: Ratio Radio printable.
Print a copy of the Answer Key: Conversions Rock Worksheets printable for your own use.

Lesson Directions

Introduction to New Material

Step 1: Remind students that fractions, decimals, and percentages are all ways of expressing parts of a whole. Start a basic review lesson by drawing a square on the board.

Step 2: Draw a line vertically through the center of the square drawing. Ask students what fractions you have drawn. (The answer is 1/2 and 1/2.)

Write an equation on the board showing how two halves added together equal a whole. For example, 1/2 + 1/2 = 2/2 or 1

Step 3: Point out that sometimes it can be easier or more natural to convert fractions into a different format, such as decimals, for certain calculations. Ask students to think of a real-world situation in which this might be the case. Examples might include converting fractions to decimals when discussing money: If a younger sibling says he or she found five pennies on the ground and calls this 5/100 dollars, it would be easier to understand if you converted to 0.05 dollars, which can easily be understood as 5 cents.

Step 4: Ask students how the same part-to-whole relationship in the square on the board could be expressed using decimals. (The square drawing shows 0.5 and 0.5.)

Note that 0.5 + 0.5 = 1. Indicate that one way of thinking about fractions is that they are division problems, with the numerator as the dividend, the denominator as the divisor, and the fraction bar as the division symbol. To calculate the decimal equivalent of a fraction, simply divide the numerator by the denominator. So 1/2 is 1 ÷ 2, which equals 0.5.

Step 5: Ask students to show the same relationship using percentages. (The answer is 50% + 50% = 100%.)

Tell the class that the word percent means “out of 100.” To calculate a percentage equivalent from a fraction, first find the decimal equivalent and multiply by 100. Show how this can be achieved by moving the decimal point two places to the right. For example, 1/2 = 0.50 = 50%.

Step 6: Draw another line horizontally through the square, cutting it in half again. Ask students to describe one of the 4 equal pieces as a fraction (1/4), as a decimal (0.25), and as a percent (25%). Then draw two lines diagonally through the center of the square to create 8 equal pieces. Ask students to describe each piece as a fraction (1/8), a decimal (0.125), and a percent (12.5%).

Step 7: Tell students that some fractions are not as easy to convert into decimals and percentages. For example, draw an empty box again and divide it into 3 equal bars. Ask students to describe a piece as a fraction (1/3). Now ask them to show the piece as a decimal and as a percentage. The answer is 1 ÷ 3 = 0.3 or 33.3%. Explain that a line drawn over the top of a number means the digit repeats infinitely.

Step 8: Remind students that when adding fractions, the fractions must have common denominators. For example, when adding 1/3 and 1/2, convert 1/3 to 2/6 and convert 1/2 to 3/6. (The sum is 5/6.)

If necessary, remind students how to convert fractions to an equivalent by multiplying or dividing the numerator and the denominator by the same amount, e.g., 1/3 becomes 2/6 when the numerator and denominator are multiplied by 2.

Guided Practice

Step 9: Group students into pairs and ask them to convert the fractions 1/5 and 1/6 to decimals and percentages. (Answer: 1/5 = 0.2 = 20%. 1/6 = 0.16 = 16.6%)

Independent Practice

Step 10: Distribute the Conversions Rock Worksheet: Stardom: Just a Fraction Away printable for classwork or homework for students to complete.

Step 11: Check for Understanding: Review the answers with the class using the Answer Key: Conversions Rock Worksheets printable.

Step 12: For additional reinforcement or practice, distribute the Conversions Rock Bonus Worksheet: Ratio Radio printable. Review worksheet answers with the class using the Answer Key: Conversions Rock Worksheets printable.

Lesson Extensions

Real-World Math Extensions

One or both extensions could be used in conjunction with any of the three lessons in the Conversions Rock unit, as the teacher sees fit.

Ask students if they can think of professions that involve math. Discuss with students what an actuary is. Actuaries use statistics in their job to calculate risks for many different industries, and they look at data in terms of fractions, decimals, and percentages. Actuaries also use ratios and proportions in predicting the likelihood of events. For example, by analyzing past experience, an insurance company determines that 1 in every 20 drivers will have an accident in a given year. If they insure 10,000 drivers this year, the insurance company can plan ahead and put aside money to pay for 500 accidents (based on the proportion 1/20 = 500/10,000).
The Series of Unfortunate Events books contain types of events for which actuaries may estimate the likelihood of occurring. For example, they may find that 1/3 of all skiers have accidents. Or that 40% of all skydivers injure their feet. Or 0.20 of all residents in a Kansas town have experienced tornado damage. Can you think of other events actuaries might analyze?

Post Instructional

Standards

Grade 7: Multi-Step Real-Life Problems With Fractions, Decimals, and Whole Numbers (CCSS 7.EE.B.3)
Grade 6–8: Constructing an Argument, Modeling, Using Appropriate Tools, Attending to Precision (CCSS MP3–6); NCTM Number and Operations

For more information, download the comprehensive Standards Chart: Conversions Rock printable.

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