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Trading floor · 7/8Higher or Lower
Desk · bankroll Streak 01,000
Current card ·
Your stake:
Cards left, by rank
20%
Briefing · Trading floor

Higher or Lower

Skill: conditional probability, Kelly sizing, ruin

A card is shown. Call whether the next card from the same deck is higher or lower, and choose what share of your bankroll to bet at even money. Ties lose. The deck is not reshuffled, so count what has gone.

p(higher) = cards left strictly above ÷ cards left bet f* = 2p − 1
Shorthand
  • On a 7, both sides are ~46%. Ties make it a losing bet. Stake 0.
  • Count the deck. After many low cards, "higher" gets better even from a 6.
  • Stake = 2p − 1. A 2 showing: p ≈ 0.92, Kelly ≈ 84%. Half-Kelly ≈ 42%.
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