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'Four Coloured Lights' printed from http://nrich.maths.org/
Imagine a machine with
four coloured lights and a keypad for entering numbers.
Each light responds to a
different rule. When a number is typed in, lights go on if their
rule is satisfied. If the number satisfies more than one rule, then
more than one colour will light up.
Your challenge is to find
the smallest possible number which will make all four colours light
data which have been collected about the responses from the
machine. Try to make sense of the information and figure out the
rules used by the machine.
A second machine works in
the same way but according to a different set of rules. Here
data from the second machine.
Send us your solution for a number which will turn on all the
lights, with an explanation of how you arrived at your answer.