How'd You Get That Many?
Students will be able to solve addition word problems with three whole numbers whose sum is less than or equal to 20.
- Call students together.
- Ask students to think about a time when they have needed to use addition, or answer an addition question, in their everyday lives. Students may suggest times they have counted something, spent money, or cooked food.
- Ask students how they knew that they needed to use addition in these situations.
- Discuss and guide students to the fact that addition is used when you combine things together.
- Tell students that today they will be looking at real life examples of problems requiring addition. They will know that they need to use addition, because there will be groups of things that need to be joined together. They may also notice certain words like “more,” “added,” and “plus,” which indicate addition in word problems. The questions asked may be about “totals” and the number “altogether,” which is another indicator of an addition problem.
Explicit Instruction/Teacher modeling(10 minutes)
- Tell students that you had a problem getting to school today. 3 buses broke down in front of your bus, 2 bicyclists were riding on the sidewalk and fell in front of you, and 5 dogs blocked your way. Your friend has asked you how many problems total you had getting to school today, and you’re wondering if they know how to give her an answer. Students should realise that this will involve adding up all the problems that occurred. If not, guide them to this conclusion.
- Ask students for suggestions of different ways they could find the answer to your friend’s question. List any suggestions students provide and then include any additional ones necessary so that the list mentions using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
- Demonstrate each of these methods for students. Use manipulatives to represent the buses, bikes, and dogs, draw a picture of all the buses, bikes, and dogs, or write an equation that shows 3+2+5=?
Guided practise(10 minutes)
- After finding an answer to your friend’s question, pass out the How’d You Get That Many? practise sheet.
- Tell students that they will be working on this alone, or in partners if you prefer, but you are going to do the first problem together as a class.
- Read the first problem aloud to students. Ask students what they will need to do to find the solution.
- Ask student volunteers to demonstrate solving the problem using manipulatives, a drawing, and by writing an equation with a symbol for the unknown number.
- Help students to solve the problem these three different ways and come up with an answer to the question.
- Ask students if they have any questions before they begin working on their own. Remind students to use the problem solving methods they have seen demonstrated in class.
Independent working time(10 minutes)
- As students work, any adults should be circulating answering questions and correcting misconceptions.
- It may be helpful to designate portions of the classroom for different problem solving techniques and have students rotate between these sections as they solve their word problems. Depending on student reading ability, it may also be necessary to read all of the problems aloud as a class.
- Enrichment:For students needing a greater challenge, incorporating elements of subtraction can add to the difficulty. Including additional numbers in the wording that are not needed to answer the word problem can also add to the challenge.
- Support:For students who need a little extra assistance, leaving the brainstormed list of problem solving techniques in a prominent area can be useful. Providing partners for the activity can also help to scaffold it. Additionally, presenting the word problems with pictures, large text, and extra spacing can make the task seem less intimidating.
- Students can be assessed based on the accuracy of their work during independent work time. Student work should not only be correct but demonstrate a variety of problem solving methods.
- For homework, students can be assigned additional word problems. Once again, accuracy in solving the problems and the ability to apply a variety of problem solving methods should be evident.
Review and closing(5 minutes)
- Call students together.
- Ask students to reflect on the word problems. Which one(s) did they have the hardest time with? Why? What problem solving technique did they find most helpful?
- If students seem to have struggled with any problem in particular, take time to go back over that problem as a group. Demonstrate how to solve it using a variety of problem solving techniques.
- Remind students that certain words like "altogether," "total," “more,” “added,” and “plus” indicate addition in word problems. Students can apply a variety of problem solving techniques like using physical objects, drawings, and equations to solve these problems.