# Finding 10, Finding 20

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## Objective

SWBAT fluently identify complements of 10. SWBAT fluently identify complements of 20.

#### Big Idea

The students will work on teams of two or three to work on their ability to fluently identify complements of ten or twenty.

## Warm Up

10 minutes

I start today's lesson by handing each student a small student clock. I have a bigger demonstration clock.  It has been a few weeks since we have worked on time concepts and I want to review and keep the skills fresh.

I start by asking the students different hour and half hour times.

"I am going to say a time out loud.  I want you to use your own clocks and set them to the time I say.  Once you have it set, keep it against your chest until I ask for everyone to show their clock."

I repeat this several times.  If I feel someone is is struggling, I will ask them to show me their clock as they set the time.  Here is a video, Warm Up With Clocks, that models this activity.

In this situation, the students are telling times to hour and held hour increments.  They are able to read the analog clock and set the clock to a given time.  This meets the CCSS expectation for first grade students (CCSS.MATH.CONTENT.1.MD.B.3).

## Introducing New Activities

10 minutes

Note:  I am going to introduce two activities.  However, each of these activities can be played with a focus on complements of ten or complements of twenty.  I will introduce the games with a focus on the complements of ten and then quickly discuss how it would work for twenty.

Advanced Preparation:  You will need to make copies of Math Pairs to 10 and Math Pairs to 20 for today's lesson.  I would make enough for each student to play the games two or three times.  You will also need 0-9 dice and 1-20 dice.  If you don't have these dice, you can make spinners to use instead.

"I want to introduce you to two new activities today.  One activity is called Math Pairs to 10.  In order to play this game, you will have to use this recording sheet (show them the Math Pairs to 10 sheet).  This game will be played in teams of two or three.  You will also need a different colored crayon for each player.  Player 1 must find two numbers that make ten but they must be adjoining squares (you may have to define adjoining).  Then the next player finds another complement of ten.  You continue to play until someone can't make a move."

"All of you know your tens and I want to just work on for fluency with them.  So I will ask some of you to start with complements of ten. I will ask the remaining students to play the same game but using the Math Pairs to 20 sheet and focusing on complements of 20."

This will be one of your choices today.

"The second game is called Rolling For Ten.  To play this game you will also play with a partner. You will need a 0-9 die.  The first player rolls the die and looks at the number rolled (keeping it covered from your partner).  You then have to think of the complement that goes with the rolled number and state that number.  Your partner will then have to state the number you rolled based on the number you stated.

Let's say I roll a 4.  I would say "6" to my partner because 4+6 are a complement of 10.  My partner would then have to figure out what goes with 6 and state 4.  He/She can check their answer by looking at the numbered rolled."

Partners then take turns being the roller.

"If you are someone who is working on the complements of 20, you will play the same game but use a 1-20 die instead of a 0-9 die.  Again, I will let you know which complements that I want you to work on."

## Station Time

30 minutes

Students have the choice of either station activity for their focus. I will let them know if they are working on complements of 10 or 20.  This decision is based on testing and observations that I have made throughout the year.  Although all of my students know their complements of 10, I want to make sure that they can produce them fluently.  Therefore I will start some kids with 10s and others with 20s.

If the student is working on complements of 10:

Rolling For Ten:  This activity is was just introduced in the previous section of this lesson.  Students can play this game for as long as their interest is held.  Then they can switch to the Finding Ten activity.

Finding 10s:  This activity allows for the same fluency practice as the dice activity. If the student is working on complements of 20.

Rolling For 20:  This activity is was just introduced in the previous section of this lesson.  Students can play this game for as long as their interest is held.  Then they can switch to the Finding Twenty activity.

Finding Twenty: This activity allows for the same fluency practice as the dice activity. If the student is working on complements of 20.

These activities have students fluently adding within ten and building fluency within 20.  This is a CCSS expectation for first graders (CCSS.MATH.CONTENT.1.OA.C.6).

## Lesson Wrap Up

10 minutes

I gather the students back on the carpet and have them face the whiteboard easel.  The focus of this conversation will be to develop fluency with two addend combinations of 20.  I will review the connection of complements of 10 to complements of 20.

"Today all of you had a chance to play a game that focused on complements of 20.  In both of today's activities you needed to find two numbers, or addends, that make 20, like 10+10 (I write this on the easel Ways to Make 20).  What other combinations of 20 did you find while you played?"

After a few examples are offered, I ask them what if we wrote 19+1 on the board. What could we write next?  I continue until all of the combinations are listed.  I then ask them about the turn around facts and write them next to the first set of facts (Ways to Make 20).

I finish by focusing on the teens and ones numbers that make 20.  You can see on the poster, Ways to Make 20, that I drew lines to show how the ones in each number make a new group of ten.  The students are using their knowledge of complements of 10 to solve for 20.  This is an example of students using prior math knowledge to solve new problems (CCSS.MATH.PRACTICE.MP4).

## 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.