Converting Metric Measurements to Decimals & Fractions
Students will be able to convert decimals to fractions in denominations of 10 or 100.
- Measure a pen to the nearest centimeter (a metric fractional unit of length = 100th of a meter) in front of your class. Highlight how to begin measuring with a ruler at zero, not one.
- Have a student write the measurement amount where the whole class can see it. (An average pen is about 30 to 40 cm.)
- Next to the answer, write the following conversion, from centimeters to meters (the standard unit for measuring length in the metric system):
- 10 centimeters = 0.10 meter
- 0.10 meter = 10/100 meter
- Referencing the conversion information, tell your students to think, pair, and share their thoughts on how long the pen would be in meters (expressing any patterns, clues, or observations).
- Have students share out their ideas. Encourage your class to use patterns, clues, or observations in their explanations.
Explicit Instruction/Teacher modeling(10 minutes)
- Demonstrate how the pen's measurement conversion from centimeters to meters is done by moving the decimal two places to the left. (This is a pattern; i.e., an 18 cm pen is converted to 0.18 meters = 18/100 meters.)
- Note how this algorithm makes sense, being that centimeters are smaller units, or a fraction of the larger meter units.
- Show your class a meter stick and point out the centimeter and the meter measurements.
- Tell your class today’s lesson objective is to practice converting amounts in smaller units into larger units. Specifically, students will describe centimeters as fractions of a meter to the tenths or hundredths.
Guided Practice(10 minutes)
- Have your students consider the pen measurement situation and ask them how long two pens measured together would be in centimeters and meters. (In other words, 18 cm x 2 = 36 cm or moving the decimal two places to the left, this equals 0.36 meters or 36/100 meters.)
- Take student answers and have them explain their answer in terms of centimeters. Call on a mix of students to explain each step of the conversion to meters process. Take note of the pattern of how the decimal moves two places to the left when converting from centimeters to meters.
- Have a student remind the class why this makes sense (because centimeters are a fraction of the larger meter units). Explain how it helps to always ask, "Does this answer make sense?" when finishing a problem.
Independent working time(15 minutes)
- Hand out and preview the Wedding Stationery Conversions worksheet with your students.
- Answer any clarifying questions as needed.
- For students who need more practice, extend the guided model lesson to other objects in the class.
- Post the opening model situation on poster paper throughout the lesson for student reference.
- Have students write the guided lesson example in their math journals for reference.
- Have students extend conversions in different denominations like kilometers and millimeters.
- Apple Clips is a great free downloadable application for the iOS that allows you to make brief movie presentations with pictures, text, and sound. For Mac users, it makes for quick, easy, and engaging audio visual presentations.
- Create a station with a metric ruler and several items on a table for students to measure. Give students the option to choose an item of their choice to measure.
- On a slip of paper, have them write their name, item, and measurement (with conversions from centimeters to meters in decimal and fraction form).
- This station may be used as an exit ticket in which they submit their calculations for review.
Review and closing(10 minutes)
- Review answers with your students by having them share out to the group. Audience peers may challenge presentation explanations by "begging to differ" and presenting their conclusions or disputes.
- Post any patterns, generalizations, or academic terminology students use in the closing for further reference.