This problem is an easily understood task so everyone can get started. It encourages children to think about the construction of the familiar hundred square and about the first one hundred numbers in our counting system. However, children may need to work on their resilience and perseverance skills as they
may discover it is not quite as straightforward as it first appears!
As they test out their ideas and become even more curious about the construction of this coded hundred square, encourage learners to offer conjectures, and to explain and justify their ideas.
This problem featured in an NRICH Primary webinar in September 2021.
You could introduce this problem first by asking the group to picture a 'standard' hundred square in their mind's eye. Challenge them to answer questions orally such as:
Where could we start?
What might the first row of numbers look like? Why?
How might the highest number look different from the others?
What do you know about the multiples of 11?
What will be the same in each column?
What will be the same for the first nine numbers in each row?
What could you do if you are stuck?
Some children may benefit from having a standard hundred square to refer to as they work on this problem. It might help to try this Hundred Square Jigsaw first.
Learners could have a go at Hundred Square, which will furthre deepen their understanding of the structure of the number square and our number system generally. They might also like to try Alien Counting, which introduces different bases, or Which Scripts?, which looks at numbers in different languages.