Show that any purely periodic proper fraction equals a fraction whose numerator is the period and whose denominator is 10^r − 1 (a number of r nines), where r is the period length.
Convert to decimal form:
23/99
1234/999,999
B. Repunits and divisibility
In the sequence 1, 11, 111, 1111, …, how many of the first 100 terms are divisible by 13?
If a repunit 11…11 (all digits
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