Semaphore

I am standing behind five pupils who are signalling a five-digit number to someone on the opposite side of the playground. What number is actually being signalled?
Age
11 to 14
Challenge level
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Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

 

Semaphore



I am standing behind five pupils who are signalling a five-digit number to someone on the opposite side of the playground.

From where I am standing the number looks like 23456.

What number is actually being signalled?

 

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.