Fermi Estimation
Give a range you are 90% sure contains the answer.
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60s per question. Less time means rougher anchors and braver intervals.
Scoring
Each question starts at 100. Every 10x of width costs 20: a 2x range keeps 94, 10x keeps 80, 100x keeps 60.
Outside your range: a steep extra cost. 25% outside costs 39 more, 2x outside costs 120 (the floor is -100).
Skip, or time out with nothing typed: -50.
Your score is the average per question. 70 or more clears the tier.
Aim for your honest 90% range: narrower misses too often, wider pays for the width.