Decimal expansion of 1/p, where p is prime - length of repeating sequence?

I appreciate the thought but have to be honest - it’s all way, way beyond me. Not even close. (sigh).

I appreciate everyone’s comments but specifically want to ask Giles about what you said:

And 13 is a factor of 999999, so it repeats after 6 digits? Is that it? I thought it would be much more complicated. Thanks.