Two Digit Numbers: Even or Odd?

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SWBAT explain whether two-digit numbers are even or odd.

Big Idea

Students find strategies to determine whether two digit numbers are even or odd.


5 minutes

Yesterday we talked about what makes numbers either even or odd.  We discussed using a ten frame to decide whether a number is even or odd.  However, we only looked at single-digit numbers.  Right now, I want you to help me decide whether 12 is an EVEN or an ODD number.  You may use the cubes at your desk, your white board, and/ or a ten frame.

As students work, I circulate to discover what strategies they are using (using cubes to make equal groups of two, drawing two ten frames, looking only at the ones place,etc.) and to catch any common misconceptions. 

Introduction to New Material

15 minutes

Now that you have worked on your own, I want you to share with the group whether 12 is even or odd AND how you know.  

I Invite students to come forward and share what they think.  Some students may share that they know 12 is even because they created equal groups of 2 and found that there was no "odd one out".  Others might indicate that they drew ten frames.  Others might say that they counted by twos.  There is no right answer for how students figured out the problem and allow ever student ample time to share their strategy. 

Depending on overall student mastery, I either have students work on another problem independently or do another problem as a class. 

I ask students:  is 15 odd or even? 

When they have finished working, I have one or two students share their answer and their strategy. 

Then I ask students:  is 5 an even or an odd number? 

Students should be able to identify that 5 is an odd number.   

So both 15 and 5 are odd numbers. 

 This would also be a good time to use the same ten frames we used yesterday--students will see that 15 is made up of 10 and 5. Since ten is even they only need to look at the "leftovers" (5).  

Let's look at 12.  We know that 12 is an even number.  Is 2 an even or odd number?  

Students should be able to identify that 2 is an even number.

Turn and Talk: What pattern do we notice when we look at these numbers?

Some students might struggle to notice that they need to look at the ones place in order to identify whether a number is even or odd--allow them to think carefully about what pattern is present and struggle with not knowing.  

I allow any student who has identified a pattern to share out.  

I push students to consider the pattern more deeply by asking them: Do you think 22 is an even or odd number?  How about 32?  How do you know?   

So, I know that both 15 and 5 are odd and both 12 and 2 are even.  I think this might mean that I only need to look at the ones place to determine whether a number is even or odd.  Why do you think that might be? 

If students are struggling to determine why this rule holds, encourage them to think about whether ten is an even or odd number.  Students should be able to identify that since 10 is always even, they only need to look at the ones place. 

Guided Practice

5 minutes

Now, we are going to do a few practice problems on our white boards. I  am going to write a number on the board and I want you to use your white board to determine whether that number is EVEN or ODD.  

I show between 2 and 6 two-digit numbers. After each number, have one student share their work. For students who are struggling, I support them by circulating and reminding them of what we discussed during the independent practice. 


Independent Practice

10 minutes

Independent Practice differentiated base on proficiency with this subject (I use yesterday's independent work or mastery during guided practice to determine groupings).


Group A: In need of intervention

Students in group A will determine whether numbers 8-20 are even or odd using cubes, white boards, and/or counters.  Having a concrete representation of the numbers will allow them to more deeply understand whether numbers are even or odd.  NOTE:  Do not have students in group A only look at the ones place if they cannot explain why they are only looking at the ones place. 


Group B: Right on track! 

Students in group B will determine whether numbers 10-30 are even or odd.  They can use a ten frame and/or a white board to help explain their thinking. 


Group C: Extension

Students in group C will determine whether numbers 10-50 are even or odd.  Since these students will likely have a more abstract understanding of the concepts, they will not use manipulatives.  During my time with this group, I will also work with them to discuss counting by 2s as a way to determine whether a number is even or odd. 


5 minutes

In order to show what we know, we are going to work on an exit ticket.   Work silently on your exit ticket so I can tell exactly what you know. 

As students work, circulate to determine student mastery.  I will use these exit tickets to determine my A/B/C groupings for independent work tomorrow.