B2.5 Add and subtract fractions with like denominators, in various contexts.
Activity 1: The Race
Present the following scenario to students:
As part of his training for a race, William must run at least 6 1/10 km a day. This morning, before going to school, he ran 3 1/10 km. How many kilometres does he need to run after school?
Ask students the following questions:
- How can you represent the situation? Which model helps you the most?
- How would you explain how you use the model to solve the problem to someone who has never used it before?
- How do you treat the whole number parts in this situation? The fractional parts?
- What might be a similar situation?
Source: adapted from Guide d'enseignement efficace des mathématiques de la 4e à la 6e année, p. 93.
Activity 2: Ben's Party
Kim, Leo and Suki are guests at Ben's house. His mother offers them some cake. Leo eats 2/6 of the cake. Ben, Kim and Suki each eat 1/6. Ben's mother is worried that she won't have enough cake for Ben's grandparents, so she takes out 3/6 of another cake.
- What fraction of the cake did the friends eat?
- What fraction represents the amount of cake left before Ben's mother takes out more?
- What improper fraction and what mixed number represent the total amount of cake available at the party for Ben's friends and grandparents?
Source: En avant, les maths! 5e annnée, ML, Nombres, p. 7-8.