More Cake Halves

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SWBAT create halves of squares and cakes. SWBAT explain that a whole split in halves has two equal pieces.

Big Idea

Students will continue to explore the concept of half.

Warm Up

5 minutes

I have the students gather in a circle on the carpet.  I give them each analog clock I will use the white board to write down digital times.

"I will write a time on the board using digital notation.  Your job will be to set your clock to match that time.  when you are finished, you should hold up your clock so that I can see your answer."

I repeat this with hour and half hour times.  

At this point in the year, I am reviewing established routines and concepts from the year long curriculum. This activity is meant for students who are familiar with the use of a clock and understand the basic time concepts. I also think it leads nicely into a discussion of fractions because the clock has vocabulary that students need to learn that connects to concepts of halves and quarters (half past, quarter past, etc.).

This activity has students telling and writing times to hours and half hours.  This meets the CCSS CCSS.MATH.CONTENT.1.MD.B.3.

Folding Paper Squares

15 minutes

Advanced Preparation:  You will need to cut out a bunch of blank paper squares.  

"Today we are going to continue talking about halves and what it means to divide something in half.  If i take this square (one square sheet of paper) and ask you to fold it in half, what will happen to it?  What can you tell me about the pieces that will be created?"  

"I would now like you to take two squares of your own and fold them in half (two different ways).  When you are done, we will take a look at how each of you folded your squares."

  • I want students to end up seeing that a square can be folded down the middle to create two equal sized rectangles or folded down the diagonal to create two equal triangle pieces. I will encourage them to conceptualize that these are the only two ways to cut a square into two equal pieces or halves. Other ways would result in unequal pieces that wouldn't meet the criteria for the concept of half.

"Who could show us one way they folded a square to cut it in half (see Folding in Half)?"

I will then post each (different) example on the board so that students can see the different ways of cutting a square in half (see Folding In Half).  I will also label each half with the 1/2 notation.

Again, the main purpose of this activity is to establish that things that are cut in half have two EQUAL pieces.  

Making Half Cakes

30 minutes

Advanced Preparation:  You will need to make enough copies of Square Cakes for each student.

"I am going to ask you to be bakers again and create more cakes using the Square Cakes sheet.  I want you to find as many ways to divide your cakes in half and use marker to "frost" your cakes."  I want you to use a different color for each half of the cake.  As you are working, I will come around and talk to you about your cakes."

I have included a video, Explaining His Thinking of Halves, that captures a student explaining his work in a precise way (MP6).

This activity has students partitioning squares into two equal shares, describe the shares using the words halves, and the phrase half of.  They are also asked to describe the whole as two of the shares (CCSS.MATH.CONTENT.1.G.A.3).

Lesson Wrap Up

10 minutes

As students are cleaning up from the Creating Half Cake activity, I quickly sort their cakes (by how they were divided) and create a poster with them (Class Halves Collection).  

"I want you to look at the collection of cakes that our class made.  There are a variety of ways that the cakes were divided in half.  However, no matter how they were cut, what can you say about each half?"

The idea is that students walk away understanding that two halves make a whole and that each half is the same size.

"I now want you to work on this sheet, Finding Halves, on your own.  This will allow me to see who understands the concept of half."

Continued Practice

5 minutes

I will ask the students to meet me on the carpet and hand out their sheet for today's Mad Minute exercise.  This routine was introduced in a previous lesson.  Please check out the link to get a full overview of this routine.

I want to really focus on fact fluency and build upon the students ability to solve within ten fluently (CCSS.MATH.CONTENT.1.OA.C.6).  I am going to use the Mad Minute Routine.  This is a very "old school" routine, but I truly feel students need practice in performing task for fluency in a timed fashion.  Students need to obtain fact fluency in order to have success with multiplicative reasoning.  Students who don't gain this addition fact fluency by the end of 2nd grade tend to struggle with the multiplicative reasoning in third.  Having this fluency also allows them to work on more complex tasks because the have the fact recall to focus on the higher level concepts.