How Big is Your Tower?
Students will be able to compare towers to explain patterns of one less.
- Show students a tower of five snap cubes.
- Ask, “How many cubes do I have in my tower?”
- Count aloud with students.
- Now ask, “How many cubes would I have if I had one less?”
- Have students share a few answers, then take away one cube.
- Count how many cubes are left.
Explicit Instruction/Teacher Modeling(5 minutes)
- Write on the board 5 - 1 = 4. Tell students that five take away one is four.
- Say, “Five is one less than four.” Use snap cubes to show what that means.
- Point to the number five on the number chart. Move your finger one space to the left and say 5 - 4 = 1.
- Explain that numbers that are next to each other on the number chart are one more than each other. Because five is one more than four, that means that four is one less than five.
Guided Practice/Interactive Modeling(10 minutes)
- Hand out snap cubes to the students. Have them each make a tower of four cubes.
- Ask your students to make a tower of one less than four. Instruct students to take one cube off of their towers.
- Ask students to turn and talk to a partner about how many cubes are left in their towers.
- Ask, “How many is one less than four?”
- Have students turn back to the number chart to see that four is one more than three, so three is one less than four.
Independent Working Time(15 minutes)
- Pass out paper to students. On the board, write: 5 - 1 = 4 and 4 - 1 = 3.
- Have students make their own number towers, then subtract one. For each tower they make, they should write a subtraction number sentence to match.
- Show students how to write number sentences using the frame ___ - ___ = ___.
- Explain that their number sentences should all match the frame ___ - 1 = ___.
Enrichment: Have students solve subtraction problems by using snap cubes and locating the related numbers on number charts and/or number lines.
Support: Limit students to working with five, seven, or 10 snap cubes.
- Assess students’ understanding by observing how they are noticing patterns as they subtract one.
- Look at their papers to see how they solved the subtraction problems.
Review and Closing(5 minutes)
- Have students share some of their number sentence and notice patterns of one less.