Doubling Fives

This activity focuses on doubling multiples of five.

Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

Problem



This challenge is about doubling multiples of 5.

Pick a multiple of 5. Double it.

Pick a different multiple of 5. Double it.

Pick another multiple of 5. Double it.

What do you notice? What is the same about your answers? What is different?

What do you think will happen if you double another, different, multiple of 5? Try it!

Will your noticings always be true? 

Test out your ideas by trying some more examples.

Mathematicians aren't usually satisfied with a few examples to convince themselves that something is always true.

Can you create an argument that would convince mathematicians?