Missing Numbers

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SWBAT identify patterns on a hundreds chart. SWBAT use patterns and structure of the hundreds chart to identify missing numbers.

Big Idea

Young children love a good mystery. This lesson allows them to explore numbers to 100 and how they are structured on a hundreds chart while playing a really fun and engaging Missing Numbers game.

Objective and Hook

8 minutes


You counted to 100 all the time in K. Let’s sing a song to help us remember how we counted to 100!

Get fit and count to 100 song by Harry Kindergarten. Sing it two times. The first time, we will sing it all the way through. The second time, I'll explain that great mathematicians don’t have to count starting at 1, they can start anywhere and keep counting on. Start the song again somewhere in the middle, and have kids count to 100 starting at that random number (somewhere around 50).

See this link to the youtube version of Count to 100!



We are going to be using big numbers in our story problems one day so we need to get really good at counting them in order. This will help us have a number line in our brains that we can use anywhere we go!

Objective :

Your thinking job today is: How can I use what I know about a 100s chart to help me figure out missing numbers?

Opening Discussion

12 minutes

To set student engagement for the lesson, I'll start by saying, "Today I am going to try my best to trick you!! I am going to cover up a bunch of numbers and see if you can figure out what numbers are missing and then write those numbers in standard form. Before we do that though, I want us to look closely at the 100s chart."

Guiding Question: What do you notice about how the chart is set up? What do you notice about how the numbers change/stay the same?

I'll call on one student to share out to get the conversation started.


Partner Talk: What other things do you notice about how the chart is set up?

Possible Responses to listen for:

  • The chart counts by 10s (10, 20, 30, etc).
  • All the numbers start with 1 on this row, then 2 on this row, etc
  • The numbers are getting bigger as I count.
  • All the numbers have 1, 2, 3,4, 5, 6, 7, 8, 9 in them.
  • If you go backwards, the numbers get smaller.


I'll call on a few students to share ideas about what they notice and chart these ideas. 

After listing our ideas, we will chorally read the list they created.

Connect to Mystery Number Game:

  • "We noticed so many new things about how the hundreds chart is set up! This is going to help us as we work on reading and writing the numbers to 100. Remember that our thinking job is: How can I use what I know about a hundreds chart to figure out missing numbers?"
  • I will hide 1 number (students close eyes).

Guiding Question: What number is missing? How do you know?

**Push kids to articulate a coherent reason for why they know that number goes there. Start with a number under 10 to help focus them on the type of reasoning they can use**

I will hide 3 or 4 more numbers and follow this same routine.

Game Rules and Practice

10 minutes

I'll present the game to students and we will practice a few rounds together. My goal here is for students to connect the class discussion we just had with the routine of the game. 

Missing Number Rules:

  1. Partner 1 covers up 3 numbers with counters. Partner 2 can’t look!
  2. Partner 2 opens eyes and guesses a number. Partner 1 shows them the number and says, “How do you know?” or “No, the answer was ___”.
  3. Partner 2 guesses all the other numbers. Partner 1 has to ask “How do you know” or “No the answer was…”
  4. Record the numbers that were hiding in standard form.
  5. Switch! Keep playing until time is up!


I'll model a few rounds on the class hundreds chart, while also referencing the chart from earlier-“I see you know that all the numbers on this row start with a 2-we noticed that earlier on our chart”.

Guiding Questions: These questions push students to explain their thinking more thoroughly, a key aspect of MP3, Construct viable arguments and critique the reasoning of others.

  • What did ___ do to figure out the missing number?
  • Is there another way we could figure out what number is missing?
  • How would we write that number?

Independent Practice

15 minutes

Students play the Missing Number game and record the numbers they find as they go on the recording sheet in the resource section. See attached video for an example of student identifying a missing number and explaining how he knew what number was there.

Students may need different levels of support in this game. 

  • Group A (in need of intervention): These students may play on the 50 chart to make sure they are solid on those numbers first.
  • Group B (Right on track): Students will play as planned on the 100s chart.
  • Group C (In need of extension): Students will play with the 120 chart and focus on how to write those numbers. 


5 minutes

Today’s thinking job was: How can I use what I know about the hundreds chart to help me figure out missing numbers?


I will play one more round with students and close out the day.