Fractional Parts of an Hour: An Investigation

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SWBAT explain that an hour can be written as several different fractions. They will color representative segments on a clock.

Big Idea

Time and fractions are related!

Guided Practice

15 minutes

I start this lesson with a brief discussion of common units of time.   Students have usually heard 1/4 of an hour, 1/2 an hour, "I'll be ready in 10 minutes," and "Give me five more minutes."  I explain that today we'll be looking at those segments of time, and a few more, as fractional parts of an hour (MP2 - Reason abstractly and quantitatively).

As I discuss Fractions as Parts of an Hour  with them and we go through these visual examples (MP4 - Model with mathematics) I have them write the responses to the embedded questions on their whiteboards. I deliberately use Powerpoint to present this information rather than something flashier or more animated because it is so easy to stop the presentation and check for understanding.  I have students sitting in assigned spots on the carpet because that's what best suited the personality of this group and this also ensures that I usually have a clear path.  I can very quickly walk around and look at the whiteboards that I have not been able to see while I'm directly teaching.  I monitor and adjust throughout the lesson.  If only a few children need extra support, I keep moving at a faster pace and direct my individual attention to them.  If a larger portion of the class needs help, I might repeat an example or explain it in a different way.  Another strategy that works well is for a child who understands the concept to explain it to the class.  Sometimes they can understand each other when they cannot understand the way I am presenting an idea.

Here are some more specifics about how I use this presentation to facilitate the teaching of this lesson:  explanation of thinking behind ppt.

Active Engagement

32 minutes

I use one, ten and five minute increments during this active engagement and walk around to see if students are able to work with these dual concepts in mind, the idea of an amount of minutes in an hour as a fraction.

Even though sixtieths are not a 3rd grade fraction, students are very comfortable with the concept of sixty minutes in an hour, so I start everyone on this page, Minutes on Clock as Fractions. They can make use of the structure (MP7) of sixty minutes in an hour because it's a familiar concept.  Even though we don't talk about parts of an hour as sixtieths, 60 minutes in an hour is a comfortable concept.

When they move to the practice with 5 Minute Intervals on Clock, some students have difficulty with the idea that what was 5/60 in the previous activity is now 1/12.  I, of course, am delighted at the opportunity for them to be exposed to equivalencies.  For these students, I sometimes even count up by fives starting from zero, and make some kind of signal or sound effect each time we reach a multiple of five.  Anything that works to get them to understand that yes, indeed, there are 5 individual minutes in each five minute block, but since we are now counting those five as a whole group, and it only takes 12 of these whole groups to reach one whole hour instead of the 60 minute intervals, the denominator changes.  

 By the time they reach the Ten Minute Intervals on Clock most students are more comfortable with the fact that the denominator is changing because they are starting to see that the minutes are being divided up into different sized pieces of the hour.  

Wrap-up/ Homework

7 minutes

I ask students if they have any questions and I also bring up and review any common mistakes.  Then I give them HW Time as Fractions and together we complete the first problem. I'd suggest that you do that, or more if needed, before sending this home as homework.  It is important not to send this home if they are too confused.