Estimate 1/7 as a decimal. How precise can you get fast?

How to answer

About 0.143, or 14.3% (1/7 = 0.142857 repeating). In the room I say 'roughly 14.3%.' Useful anchors: 1/7 ≈ 14.3%, 1/3 ≈ 33.3%, 1/6 ≈ 16.7%, 1/9 ≈ 11.1%. Knowing the common reciprocals lets you ratio anything fast.

Key idea: Saying 1/7 is 'about 15%' when 14.3% is easy to hold, or blanking on non-power-of-two reciprocals.