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 \(6\frac{1}{10}\) km a day. This morning, before going to school, he ran \(3\frac{1}{10}\) km. How many kilometres does he need to run after school?
Ask students the following questions:
- How might you represent the situation? Which model helps you the most?
- How would you explain how you use this model to someone who has never used it before?
- How did you treat the whole number parts in this situation? The fractional parts?
- What might be a similar situation where you could use this model to solve the problem?
Source: adapted and translated from Guide d'enseignement efficace des mathématiques de la 4e à la 6e année, Numération et sens du nombre, Fascicule 2, Fractions, 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 \(\frac{2}{6}\) of the cake. Ben, Kim and Suki each eat \(\frac{1}{6}\). Ben's mother is worried that she won't have enough cake for Ben's grandparents, so she takes out \(\frac{3}{6}\) 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: translated from En avant, les maths! 5e, ML, Nombres, p. 7-8.