Where does 5 go?

 Show a number line with 0 and 10 and no intervals to investigate concepts of: equality, magnitude, sequencing, number knowledge and reasoning.

Materials: number line with 0 and 10

Clothes peg

Bus or car

“The class is going on a field trip to the zoo but there is a problem. When the bus arrives it does not have enough gas to get us all the way to the zoo. Luckily, there is a gas station halfway to the zoo. We will need to stop there and get gas. I’m wondering if you can tell me when you think the bus is halfway?”

Begin moving the bus. “Tell me when to stop.”

When a student says “stop” put the clothes peg on. Invite reasoning and discussion with class. How do you know this is or is not halfway? How can we tell for sure?

Students are given a sheet with two number lines of the same length, both 0-10.

Students are asked to use a marker or highlighter to show on the first number line how far the bus had to travel to get to the gas station.

On the second number line students are asked to show how far they think the bus would have got if it did not stop for gas. Ask students to explain reasoning to a classmate.

Key questions: How do you know your second line is more than halfway? How did you decide how far the bus would go without getting more gas? About how far do you think your second line is?  (6,7,8,9)

Problem source: mathforyoungchildren.ca