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

Problem

 

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.