Students will be able to use strategies of regrouping within two digit addition problems.
- Invite students to come sit in a large circle.
- Bring out the base-10 grab bag.
- Ask one of the students to reach into the bag (without looking) and to get a handful of base ten blocks.
- Invite that student to the centre of the circle to lead the class in counting the base ten blocks.
- If desired, you can invite all students to participate by quickly moving around the circle and having each student pull out a handful of base ten blocks for counting.
- Tell the students that they will be learning how to create base ten drawings that represent the actual base ten blocks in two digit addition. Tell the students that they will be learning how to RegroupWhich means that numbers are rearranged before adding.
Explicit Instruction/Teacher modeling(10 minutes)
- Using the example problem, 36 + 45, written as a vertical problem, use base ten blocks to model the process of adding 6 + 5To make the number 11.
- Show the students how you can turn ten of the ones into a ten and move it into the tens place. Only one is left in the ones column.
- Demonstrate the process of adding three tens plus four tens and then adding the additional ten to find the answer, 81.
- Tell the students that you are now going to repeat the problem, but this time, you will create drawings to represent the ones and tens.
- Draw small squares next to each number in the ones place.
- Draw a vertical rectangle to represent each ten beside each ten.
- When you add 6 + 5, show the students how they can circle ten ones to create a ten. This group of ten ones can then be crossed off with an X and a single ten can be drawn above the other tens.
- Demonstrate the process of counting the base ten drawings in each column to find the solution.
- Repeat the same modeling process with the following two addition problems: 29 + 48And 54 + 19.
Guided practise(10 minutes)
- Tell the students that they will be working on several regrouping problems together.
- Distribute individual whiteboards and whiteboard markers.
- Display the following problem on the board: 46 + 16And 49 + 26.
- Guide the students through the process of solving the problems by creating base ten drawings on their individual whiteboards.
Independent working time(15 minutes)
- Ask students to complete the Review Two Digit Addition worksheet and the show their work using base ten drawings beside each problem.
- Pre-teach three digit addition with regrouping. Challenge the students to complete three digit addition problems.
- Using base-ten blocks stamps and a stamp pad, have the students stamp their representations before drawing or in place of drawing if students have difficulty understanding the representations of each drawing.
- Have students complete the Regrouping: practising Place Value #1 worksheet.
- Utilize interactive base ten blocks on an interactive whiteboard.
- Use drawings or shapes on an interactive whiteboard in the teacher modeling section.
- Ask students to complete an exit card in which they create base ten drawings to solve the following problem: 17 + 25.
- If desired, ask the students to complete additional drawings on the card.
Review and closing(5 minutes)
- In a similar manner as the introduction, invite two students to take a handful of base ten blocks out of the grab bag.
- Tell the class that their task is to add the two numbers on their whiteboards by creating drawings that represent base ten blocks.
- Ask students to share their work and their thinking.
- Repeat with additional problems, as desired.
- Invite students to share any benefits or drawbacks to using this strategy to solve two digit addition problems. Ask, "How does this strategy compare with other strategies?"