Find the repeating block in the decimal of 1/13, and say how many digits it has.

Step 1. Divide. $\dfrac{1}{13} = 0.076923\,076923\ldots$ The remainders run $10, 9, 12, 3, 4, 1$, and then $10$ comes back.

Step 2. The block. $076923$, with $6$ digits.

Step 3. Two thirteenths. $\dfrac{2}{13} = 0.153846\,153846\ldots$, a different block of $6$ digits.