Recurring block

Choose powers of 10 so that the recurring digits align before subtracting. A two-digit recurring block usually requires multiplication by 100 rather than 10.

Write enough recurring digits before using an ellipsis, and mark the complete recurring block with dots: one dot for a single recurring digit, or dots over the first and last digits of a longer block.

Choose the power of 10 from the length of the recurring block: one recurring digit suggests multiplying by 10, two by 100, three by 1000, and so on.