You know that 1/7 = 0.142857. Can you predict what the decimal expansions of 2/7, 3/7, 4/7, 5/7, 6/7 are, without actually doing the long division?

Given, 1/7 = 0.142857.
Then,
2/7 = 2 × 1/7 = 2 × 0.142857 = 0.285714
3/7 = 3 × 1/7 = 3 × 0.142857 = 0.428571
4/7 = 4 × 1/7 = 4 × 0.142857 = 0.571428
5/7 = 5 × 1/7 = 5 × 0.142857 = 0.714285
6/7 = 6 × 1/7 = 6 × 0.142857 = 0.857142
Here, the first digit in the decimal expansion continued in the repeated numbers afterwards.