B1.6 Round decimal numbers to the nearest tenth, in various contexts.
Activity 1: The Shortcut
Share the following situation with students:
Youssef moves to a new neighbourhood and starts at a new school. He lives near the school and will walk to school. In order to find the shortest route, he tries some different routes.
Ask the students to round the kilometres traveled for the four different routes to the nearest tenth in order to determine the best route for Youssef to take.
Route 1: 1.88 km
Route 2: 1.79 km
Route 3: 1.96 km
Route 4: 1.85 km
Example
I estimate that Route 2 is the best since it is about 0.1 to 0.2 km shorter than the other routes.
Source: adapted and translated from En avant, les maths! 5e, CM, Nombres, p. 3.
Activity 2: The Service Station
Present the following scenario to students:
Yassim works in a service station. He has to post the price of gasoline on the sign outside.
Here are the prices he received from the station owner this week:
Monday: 149.84/L
Tuesday: 148.59/L
Wednesday: 149.85/L
Thursday: 151.21/L
Friday: 150.38/L
Saturday: 148.02/L
Sunday: 150.66/L
Present the example of the outdoor sign below and generate a discussion about it with students.
Ask students to answer the following question:
What price should Yassim post on the outdoor sign each day of the week?
Lead students to observe that gasoline prices are rounded to the nearest tenth for posting.
Allow students to use whatever strategy they choose to solve the problem.
Ask students questions such as:
- What strategy can be used to round the above decimal numbers? How do you know this will work?
- Why do you round numbers? Explain your answer.
- Do you think the numbers should be rounded up or down in this situation? Why?