# Subtracting Large Numbers within a Context

19 teachers like this lesson
Print Lesson

## Objective

Students will be able to use place value understanding to decompose numbers to subtract and solve word problems.

#### Big Idea

Students will solve subtraction problems within a context using a tape diagram.

## Warm Up

5 minutes

As students enter and get their supplies, this song is playing.

My students love this video and instantly start singing along.  Students are practicing multiples of 6 without even knowing they are doing so.  After the video I make this connection more clear for them.  I have them count out loud, 6, 12, 18, and I say stop. I also hold up a finger for each time they say a number.  I then tell them they just told me the product for 6 x 3.  I tell them that when we count by 6, or any number, we are listing the multiples of 6.  This allows me to start touching on standard 4.OA.4 in small chunks.  In the past, my students needed lots of repetition with finding factors and multiples.  This video is a fun way to start doing that.  This warm up is completely separate of skills students will use during the concept development portion of this lesson. At this point, I am content with having the warm up activity having students use a different standard or standards than than the concept development portion of the lesson because this warm up activity incorporates a grade level focus standard.

Next students work on the journal prompt of the day.  Today's journal prompt is.

Write three different six-digit numbers. Show how you would write each number in word     form, and expanded form.

I do not go over the answers together for this prompt because I want to use it as a quick assessment to see which students can use word form and expanded form. I collect their notebooks.  Students highlight the edge of the page if it has a prompt on that page. Then I mark through it once I have read it and scored that prompt.  This lets the student know I've read it, commented on it, and given them a score.

## Concept development

40 minutes

My students love this video so much, we watched it again.

This video is a great reminder about how to work with a partner since today's activity involves partner work.  My students really relate to this video, because they can all recognize behaviors in the video that they at one time have exhibited.  It's fun to see my students giggle at the characters in this video.

After the video, I give students the practice subtraction page to work on. Students continue to use Math Practice Standard 4, and model with mathematics to solve everyday problems. Students use the tape diagram as they model the word problems on the practice page and continue to make connections between their model and what is happening in the problem.

After the last lesson with word problems, I was hesitant about having students work with partners. My gut reaction was to do this worksheet all together, but upon further analysis of the problems, I thought working together might be too much support and not provide my students opportunities to have productive struggle. The problem students worked on were only one step word problems.  Since my students struggled more with two-step word problems, I made the choice to have them work with partners.  While I want to support and guide my students, I still want them to have productive struggle.  I assigned them partners to work with on the word problems.

Students spread out around the room and work to complete the word problem practice.  As they worked, I saw a lot of great things happening.  Students were talking about math! They were convincing each other that answers were correct.  They were having fun!  And, they were staying on task.  Students worked towards mastery of standard 4.OA.3 as they solve word problems posed with whole numbers and also standard 4.NBT.4 in fluently adding and subtracting multi-digit whole numbers using the standard algorithm.

Students worked on the computation side at their seats independently.  Most students finished this assignment and did not need to take it home for homework. Students that didn't finish took it home.

## Student debrief - Wrap up

10 minutes

I used an exit ticket for this lesson. Students solved one problem.  72,318 - 48,439 on their exit ticket. I chose to do a quick subtraction computation in order to gauge which students are regrouping or un-grouping correctly and which students needs more support.  As you can seen in this exit ticket image, I have five students who did not get the correct answer on the exit tickets.  The pile on the bottom right are students who came up with the correct difference.

In analyzing these exit tickets, the ticket on the top left clearly shows some big misunderstandings.  This students has un-grouped and regrouped to get 15 tens instead of 10 tens.  It is difficult to tell what numbers the student is subtracting.  This student will be pulled during my re-teaching schedule to get further support and instruction.  The ticket on the top right and the one with the difference circled in red pen both show an example of a student who appears to know how to regroup and un-group mostly, but didn't do it when they un-grouped the hundreds place and therefore have 13 hundreds instead of 12 hundreds.  These student will mostly likely benefit from some extra practice as well as seeing this problem and similar problems modeled.  The ticket with a red X on it shows that regrouping and ungrouping are carried out correctly.  The number in the thousands place is difficult to see, but nevertheless, this student can be gently reminded about writing neatly to make sure the difference is communicated.  The student who did not complete the exit ticket will need further assessed before making instructional decision since the ticket was not filled out.