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'Zargon Glasses' printed from https://nrich.maths.org/
Why do this
problem?
This problem is good for children who are confident with large
numbers but need practice in finding combinations using a
systematic method.
Key questions
What is the smallest number of lenses a family could
need?
What is the greatest number of lenses a family could
need?
How do you know you haven't got that combination
already?
Possible extension
Children could investigate what would happen if some of the
families have five eyes.
Possible support
It might be helpful for some children to use counters with either
three or four dots on to represent the eyes.