Join and Separate - It's in the Bag!

In this Remarkable Idea, students will work on their number conservation and subitizing skills

This activity addresses:

  • Beginning addition skills
  • Number conservation
  • Fine motor skills
  • Alternative methods of access

What you need:

  • Locking sandwich bags
  • Small manipulatives (bingo chips, shapes, animals, etc.) must all be the same kind.
  • Permanent marker or masking tape
  • Number cards
  • Plus symbol card
  • Equals symbol card
  • BIGmack
  • Step-by-Step


1. Prepare sandwich bags by drawing or taping a vertical line down the center of the bag.
2. If appropriate, record numbers to Step-by-Step for counting.
3. Create appropriate overlays

What to do:

1. Place manipulatives in the bag; amount will vary depending on each student’s skill level. Show the student the side without the marker or tape line, and ask the students to count how many.
2. Students count the number of manipulatives in the bag. Record this number to the BIGmack and place the corresponding number card on it.
3. Turn the bag over, and have the students separate the manipulatives into groups on either side of the line.
4. Have the student count the number in each new set they created. Place the corresponding number card on each side of the bag.
5. Show the student that the two smaller sets can be joined to make the original number by placing a plus and equals signs in the correct spaces.


“Good, you counted 5. Can you separate the set of 5 into two smaller sets?”
“Good, now we have sets of 1 and 4.” “1 and 4 make 5”

Additional suggestions:

The BIGmack should always have the original number that was in the bag recorded on it for students to reference in case they forget. The Step-by-Step should be used for counting.
This activity can also be used for subtraction by taking a separated set away.