Geometry and Measurement, Level 2
Sally the Snail crawls 2cm each minute. Sally needs to rest at each dot for 5 minutes. How many minutes will it take for her to get from the path to the plant?
(see Copymaster for picture of the path)
What is this problem about?
This is the use of arithmetic in a practical situation using time and distance.
As the calculations involved in this problem involve single digit addition and multiplication it offers a good opportunity to encourage the students' use of mental strategies.
Relevant Achievement Objectives
- Measurement AO1: create and use appropriate units and devices to create and measure length, area, volume and capacity, weight (mass), turn (angle), temperature, and time.
- cm rulers
- picture of a snail (for introduction)
- Copymaster of the problem (English)
- Copymaster of the problem (Māori)
Specific Learning Outcomes
The students will be able to:
- measure using cm.
- solve problems using minutes as the unit.
- devise and use problem solving strategies to explore situations mathematically
- Get the students to estimate 2 cm using their fingers. Ask:
What do you use to estimate 2 cm?
- Introduce Sally the snail and the time it takes for her to travel 2 cm. Ask:
Do you think that 2 cm is reasonable?
- Pose the problem for the students to work on with a partner.
- As the students work ask questions that focus them on communicating the steps they took to solve the problem.
What was the first thing you did when solving the problem?
Could you solve it another way?
How do you know that you are correct?
- Share solutions.
Extension to the problem
Get the students to create their own snail problem for others to solve. The may decide to vary the speed that Sally moves.
The snail has to travel 2 + 4 + 6 + 2 = 14 cm which takes 7 minutes. She has 3 rest stops which take 15 minutes. So the total time for the trip is 22 minutes. Some students may add another 5 minutes for the final dot but at the point Sally is already at the plant.