Lesson plan

Math Mystery Bags

Use this engaging mystery bag lesson to practice addition patterns of one more with your curious kindergarteners!
Need extra help for EL students? Try the One More Please! pre-lesson.
EL Adjustments
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Need extra help for EL students? Try the One More Please! pre-lesson.

Students will be able to compare sets to explain patterns of one more.

The adjustment to the whole group lesson is a modification to differentiate for children who are English learners.
EL adjustments
(5 minutes)
  • Introduce the lesson by displaying the number line to the class.
  • Ask the students if they know where to start when counting on the number line in order (starting with 0), then have them count from 0-20 along with you.
  • Say, "Right! When we count using a number line in order, we start at one end (point to 0) and move one number at a time to the other end."
  • Explain that today students will practice counting one more to compare groups of items.
(5 minutes)
  • Pull out two of the bags or boxes of math manipulatives and demonstrate how to find the number of objects in the bag by pulling items out one at a time and counting them. Then model thinking aloud, "I have six bears in this set. How many bears would I have if I added one more?"
  • Show students how to write number sentences using the frame: __ + __ = __
  • Explain that their number sentences should all match the frame: __+ 1 = __
  • Write up the equation 6 + 1 = __ on the board and model adding one more bear to the set.
  • Model how to add one while counting, "I had six, then I added one (look at the number line) so now I have seven!" Model how to check your work by recounting the entire set to find the total. Record the number on the board.
  • Repeat this process with the second set of items.
  • Ask the class, "Which bag has more items? How do you know?"
(10 minutes)
  • Repeat the above activity, this time inviting the students to count aloud with you and asking for volunteers to come up and finish writing the equation on the board.
  • Ask students, "Do I need to count the number of bears in the bag again before I add one more bear? Why or why not? Should I start over and say one again? Why or why not?"
(15 minutes)
  • Explain that students will now each get two bags of items and will practice counting, adding one more, and comparing their two bags to see which bag has more and which bag has less.
  • Pass out paper for students to record their equations.


  • Provide prewritten addition templates for students to use when recording their equations.
  • Pair students together to complete the activity with a partner.
  • Allow students to use their own copy of a number line when working independently.


  • Have students compare additional sets of items.
  • Provide larger sets for students to utilize.
  • Have students complete the Adding 1: Baby Chicks worksheet.
(5 minutes)
  • Walk around and assess the counting process of students as they work.
  • Ask students to demonstrate their addition equations and process of adding one more.
  • Check if students are able to accurately add one more to their set and compare two sets together to see which set contains more.
(5 minutes)
  • Close the lesson by revisiting the activity and asking students the following questions:
    • When counting, do you always have to count from one?
    • What happens if you start with another number?
    • What number comes next?
    • How do you know?

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