Subtracting Numbers

Explicit Instruction/Teacher modeling

• Use your document camera to project the number cards and explain that you will be playing a game to practice taking away or subtracting one number or amount from another number.
• Demonstrate how to play the game by placing the two card decks face down in a pile in front of you and picking one card from the top of the 5–9 deck and saying the number aloud, e.g., "I picked a 5."
• Model how to count the same number of math manipulatives as the number on the card, e.g., "I drew the 5 card from the deck, so now I am going to count out 5 cubes, 1---2---3--4---5. Now I am going to pull a card from the 0–4 deck, here is a 2 card. I am going to subtract or take away two cubes." As you model, use a think aloud strategy to share your process with the class, e.g., "How many cubes do I have left? I will count them, 1--2--3. That means 5 cubes minus 2 cubes equals 3 cubes."
• Write up the matching equation, 5 – 2 = 3, on the board and demonstrate how to read the equation to the class.

Guided Practice

• Explain that now you will get a chance to play the same game as a group.
• Draw a card from the 5–9 deck, hold it up and encourage the class to say the number aloud. Then invite the students to count chorally (or echo as needed) as you count out the matching number of manipulatives. Repeat with the second card as you model finding the difference of the two cards.
• Model how to use the cards to write a matching subtraction equation on the board and have students echo read the equation after you.
• Explain that now students will get to play the game with a partner. Demonstrate how each student will get their own deck (0–4 or 5–9) with the first student (Partner A) choosing the first card from the 5–9 deck and counting out the first set of manipulatives. Then the second student (Partner B) will choose the second card from the 0–4 deck and will subtract the matching number of manipulatives. Both partners will then work together to find the difference or remainder left.

Independent working time

• Display the Take Away the Bugs worksheet and tell the students that now they will get to practice solving some subtraction problems on their own using pictures and math manipulatives.
• Demonstrate how to read the equation and cross out the bugs to subtract.
• Pass out worksheets, math counters, and pencils to each student.