Students will be able to borrow in subtraction.
Introduction (10 minutes)
- Call students to your group area.
- Have a table with the cups (one set of 3 cups higher, one set of 3 in the middle, and one set of 3 lower using books to stack them, or tape them to your board) and your set of base ten blocks. The cups represent the hundreds (higher cups), tens (middle cups), and ones (lowest cups) place values.
- Write 2-8 on the board with 2 on top and 8 on the bottom, as in a subtraction problem.
- Ask students if they can subtract 8 from 2 while pointing at the numbers.
- When they say no, write a 1 in front of the 2 and ask if they can take 8 from 12.
- When they say yes, point out the addition of the 1 in front of the 2, which represents an addition of 10.
Explicit Instruction/Teacher Modeling (10 minutes)
- Draw a line to separate the 1 and 2 in the 12.
- Using the base ten blocks, show students that to make 12, they need one ten block and 2 ones blocks. Place them in the proper cups.
- Do the same for the 8.
- Next, show students how the 2 and 8 are in the ones column and the 1 is in the 10s column while labeling the columns above the written problem and the cups.
- Then, ask students again if they can take 8 ones away from 2 ones.
- Hold up two ones blocks if needed, and ask if there is enough in the ones column to take away 8.
- When they say no, tell them that you need to borrow from the tens place and bring a ten block over to the ones place.
- Move the ten block to the ones cup.
- Then, take 8 away from 12, and ask your students to identify the number that remains.
Guided Practice/Interactive Modeling (5 minutes)
- Repeat the previous steps again.
- Practice with various numbers, including numbers greater than 20 to show that there can be multiple sets of ten.
- Explain to your students that they can only borrow in groups of 10.
Independent Working Time (15 minutes)
- If you do math centers or have individual place value sets, set this up in centers for your students to use.
- In the center, have them use cards to decide which numbers will be in the place values. Take out any double digit cards and the face cards.
- Have them sit the cups on top of the cards and put their base 10 blocks in the cups, and then instruct them to move them around as necessary by the problem they made from the cards they pulled.
- Enrichment: Give your students numbers with thousands digits to challenge them further.
- Support: Work with your students one on one with the base 10 blocks on a few problems. Use only the ones digits until they become familiar with subtraction, and then work on borrowing.
Assessment (5 minutes)
- Give your students a basic subtraction with borrowing assessment with a few problems to make sure they get the concept. For example: 22-9, 75-26, and 14-7.
Review and Closing (5 minutes)
- Gather your class and do a few more borrowing problems on the board without the cup and card models.