# How Many Dots?

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## Objective

SWBAT count by groups of 10s. SWBAT use numbers to represent a set of objects. SWBAT add 10 or subtract 10 from a number.

#### Big Idea

Students will engage in a variety of activities that ask them to represent numbers with groups of ten and have them counting by 10s.

## Warm Up

10 minutes

Explain to the students that they are going to play a round of Popcorn.  Remember It is a counting game where you start with a number (pre-determined) and you count up until you get to the last number (pre-determined).  Ask them to stand up in a circle.  Tell the students that they are each a kernel of popcorn and ask them what happens when you heat up a kernel of popcorn?  That's right, it POPS!  Explain that today we will start with the number 10 and count to 120.  I will say 10 first.  Then the person next to me will say 20, and then the next person 30 . . .until 120.  After 120, instead of saying 130, you will say POP and sit down.  The game will continue with the very next person starting the count all over again.  The game continues until there is only one person left standing.  That person finishes the game by repeating the entire count sequence.

This activity asks students to demonstrate an understanding and/or apply an understanding of place value concepts.  Students are using  "the numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 and referring to  them as one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).(CCSS.MATH.CONTENT.1.NBT.B.2.C)"

## Introducing the Concept

15 minutes

I have all of the students sit in a circle and introduce today's focus.

"Today we are learning to (WALT)* add ten or subtract ten from a number."  Have a few students repeat the goal.  "I would like everyone to count from 20-120 (by tens) again and I want you to listen to the numbers that your are saying.  After we count, I will ask you to turn to a partner and talk about what you noticed."

*WALT (We Are Learning To) is the acronym that I use to reinforce the math focus for the day.

I will listen to the ensuing conversation and choose students to share what they noticed.  The goal is that they notice the ones don't change and the tens do.

"We just did counting on the decade, meaning we started with a tens number and counted by tens.  What would happen if we started at 4 and counted by tens off the decade?"

"Let's try this as a group.  We will play another round of POP but this time we will start at 4 and count to 74.  Let's do a quick whole group count of these numbers."

In this situation students are adding within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10 (CCSS.MATH.CONTENT.1.NBT.C.4).

Note:  Some students may still need a number line or number grid to perform the activity.  You will have to decide what is best for your students.

## Station TIme

25 minutes

***Advanced Preparation for Drop Sticks:  In order to use this activity, you will need to make sets of drop sticks. Each set consists of 10 tongue depressors/craft sticks.  On one side of each stick, you will need to draw 10 dots.  On the other side of the stick, you will need to draw one dot.

***Advanced Preparation for Building Numbers:  You will need to copy the ten frame card set for each student.  You will want to cut them out and have them in separate baggies.  Each person will need a set to play.  This is a time consuming preparation, and I have found paying my daughters to help me cut these out is a wise investment!

During station time, you will have the chance to play two games, and I want you to get to both games today.

The first game is Drop Sticks.  We have played this game before but I am going to add a new component to it today.  You will be using this Blank Drop Sticks Recording (see section resource) and this add 10 or minus ten spinner.  You should drop the sticks, and "untangle" them.  What I mean is to straighten them out but don't organize them by 10's and 1's. Once you have untangled them, I want you to try and count them in the order they are laying.  You will then write the total on the recording sheet, then spin the spinner and fill in if you are adding 10 or subtracting 10, and then write your new number.   I will now model this for you.  There is a video in the section resource that demonstrates this activity.

"The second activity is called Making Numbers.  You will read the clues on the sheet (see section resource) and mini ten frame cards to build that number.  You will then read either add ten or subtract ten (depending on what the sheet says) and record your new number.  Let's do one together."

As students are playing, I will circulate about the group, observing who students are playing the games and/or which strategy they are using to find the total amount of dots.  For students who are playing Building Numbers, I will ask them questions like:

• How many ten frames do you need to make that number?  How do you know?
• What are you doing to get your new number?

Be sure to note student strategies: adding a ten frame and recount, count 10 more on fingers, using a known fact, etc.

In these activities, the students are demonstrating that they understand or are developing an understanding that two digit numbers are made up of a group of 10's and some 1's, that numbers 1, 2, 3, 4, … 9 in each two digit number, starting with one of those numbers, represents a group of tens, and that they can start at any number and add to more to that number (CCSS.MATH.CONTENT.1.NBT.B.2CCSS.MATH.CONTENT.1.NBT.C.5).

Students are also exposed to the idea that each time the tens column is changing (when adding ten or subtracting ten) and that the ones column stays the same.  They are using repeated reasoning and/or looking for shortcuts (CCSS.MATH.PRACTICE.MP8).

## Lesson Wrap Up

10 minutes

I gather the students back in a circle and ask them to face the easel.  I then write the following on the board (see Lesson Wrap Up Image):

* 42 + 10 = 52

* 65 + 10 = 75

* 71 + 10 = 81

"What was our focus today?  What were we learning to do?  I want to make sure and reinforce the idea of adding 10 to a number.  I want you to tell me what you notice about these equations."  As students respond you should color code student responses to their observations:

• The ones place stays the same
• The tens place always goes up by one ten

What I mean by color coding is if someone says the ones place stays the same, you should circle that observation (in the equations) with one color marker and then circle the next observation with a different color.

I finish the discussion by asking the following two questions. "So what would + 10 be for 48?  What would +10 be for 83?"

In this situation, the students are reasoning abstractly and quantitatively.  Students can see that the tens place is going up by one grow each time and the ones is staying the same (with numbers up to 90).  Using this knowledge, students can start adding ten to any number (CCSS.MATH.PRACTICE.MP2).

## Exit Card

5 minutes

I end this lesson with a quick exit card.  I will use an index card for each student.  On one side I will have an addition equation that involves adding 10 to a number.  On the other side of the card I will have an equation that subtracts 10 from the same number.  Each card will be different.

"I want you to each take a card and write your name on the line.  Then I want you to quickly solve the equation on each side of the card."

## 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, as 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.