The mathematical (and other) thoughts of a (now retired) math teacher,
Friday, 19 October 2012
A Prime Airplane??? 727
Ok, you knew 7 was prime....
And you could figure out pretty quickly that 727 is prime, probably.
What about 72,727; or 7,272,727,
or even 727,272,727 ???
One of those is divisible by seven...
Is there a quick rule for which of 72727..........2727 is prime?
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