B2.4 Represent and solve problems involving the addition and subtraction of whole numbers and decimal numbers, using estimation and algorithms.
Activity 1: Representing and Solving a Problem Using Estimations
Present the following situation to the students.
Rodrigue goes to the ATM to withdraw money because he wants to buy three art supplies: a watercolour paint set for $69.97, a watercolour marker set for $149.97 and a drawing accessory set with 152 pieces for $129.99.
Ask students questions such as:
- Knowing that the "Don't Pay Taxes" event is underway, how much money will Rodrigue have to withdraw? How do you know?
- What strategies can be used to add up all the money?
- In this context, is it necessary to find an exact answer? Explain your thinking.
Activity 2: Represent and Solve a Problem Using Algorithms
Present the following race results for students of Green Mountain School.
| Student's First Name | Time |
|---|---|
| Manuela | 58.586 s |
| Leo | 1 min 11.358 s |
| José | 59 214 s |
| Yoani | 1 min 2547 s |
| Louis | 47 914 s |
| Yasmin | 55 602 s |
Ask students questions such as:
- How many seconds are there between first place and second place? Second place from third place? First place from third place? How do you know this?
- What strategies could be used to compare and subtract decimal numbers? Explain your choice.
- In this context, is it necessary to find accurate answers? Explain your thinking.
Compare the students' different algorithms. Find similarities and differences between the various algorithms. Ask students to explain their mathematical reasoning.