Units of Time

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SWBAT convert from one unit of time to another unit of time by multiplying or dividing.

Big Idea

A table can be used to model converting between units of time by multiplying or dividing.

Whole Class Discussion

15 minutes

To begin the lesson, I review with the students the various types of measurement that we have already covered. We have studied the customary units of weight, length, and capacity.  We have also learned about the metric units of weight, length, and capacity.  Today, we will study the units of time.  We will convert units of time from one unit to another unit (4.MD.A1).

What are units of time?  Student responses:  years, months, days, hours, minutes, and years.  I let the students know that they are correct.  I remind them that these are units that they should have learned in lower grades.  I share with the students that today, we discuss new units of time that may not be familiar to them.  

On the Smart board, I display the units of time chart.  I let the students know that, just as we did with the customary units and the metric units, we will convert between different units of time.  Together, we identify things in the chart that are familiar to the students.  As we discuss the units that the students know, I give examples.  For 1 week = 7 days, I give the example, "Susan drove 10 hours a day for 1 week.  The chart tells us that 1 week is equal to 7 days.  Therefore, we multiply 10 x 7 to get a total of 70 hours." I also discuss with the students that in a leap year, we add the extra day to the month of February.  (I want to make sure my students are exposed to information that we sometimes think that they should know.)  Next, we identify the units that are new to the students.  Those units are decades, century, and  millenium.  I say the word, then have the students repeat it.  (I like to keep the students involved in the whole class discussion by using questioning and choral responding.  It keeps them focused on the lesson.)  

I let the students know that we can convert from one unit to the next using a chart.  For example, 7 weeks = ____ days, we can go to the chart to help us solve this problem.  I ask the students to read out the information from the chart that will help us solve this problem.  Student response:  1 week = 7 days.  We know that we can make a table to help solve this problem.   The students help to fill in the table.  I remind the students that the first number tells us what to count by, and because it is repeating, this is multiplication.  

















There are 49 days in 7 weeks.

I reiterate to the students that going from a larger unit to a smaller unit, you multiply.  (I remind the students of the example of going from a gallon of milk to quarts.  It will take more than 1 quart to hold the entire gallon.)  For this problem, we multiply 7 x 7 to get 49.  If we go from days to weeks, we should divide.  




Skill Building/Exploration

20 minutes

For this activity, I let the students work as pairs to convert units of time.  By doing this, it allows the students to hear their classmates thinking on the skill (MP3).  

I give each pair a Units of Time activity sheet.  The students must convert from one unit to another by using strategies such as multiplying, dividing or drawing a chart (MP4).  The students are required to work together on each item.  As the pairs discuss the problem, they must be precise in their communication within their groups using the appropriate math terminology for this skill (MP6). As you hear in the video, the students must use reasoning and strategies to find their answers.

As they work, I monitor and assess their progression of understanding through questioning. 

1.  What does the unit of time chart tell us?  

2.  What strategies can you use to find the equivalent number?

3.  Are you converting from a smaller unit to a larger unit or a larger unit to a smaller unit?

As I walk around the classroom, I am questioning the students and looking for common misconceptions among the students.  Any misconceptions are addressed at this point, as well as whole class at the end of the activity.

My Findings:

Because we have practiced converting units of capacity, weight, and length for both the customary and metric units, the students are doing quite well with this task.  The one problem that I noticed as I walked around was that the students were having difficulty with problem 1: 38 days ____ 2 months.  Some of the pairs skipped this problem and went on to solve the other problems.  This problem caused difficulty because the chart does not identify "days to months."  Therefore, some students had a difficult time converting this.  In the Video - Units of Time, you can hear as I questioned one pair of students to help guide them to the answer.  


15 minutes

To close the lesson, I bring the students back together as a whole class.  I feel that it is very important to let the students share their answers as a whole class.  This gives those students who still do not understand another opportunity to learn it.  

I feel that by closing each of my lessons by having students share their work is very important to the success of the lesson.  Students need to see good work samples (Student Work - Units of Time), as well as work that may have incorrect information.  More than one student may have had the same misconception.