# Snails

## Geometry and Measurement, Level 2

### Problem

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.

### Resources

- 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

### Teaching sequence

- 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.

#### Solution

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.