Mathematical expectation is simple: multiply probability by value, and choose the larger one.

Option A: A 100% chance to win 100 RMB, expected value is 100.

Option B: A 1% chance to win 20,000 RMB, expected value is 200.

Choose B, not A.

Life is a long series of bets. You’ve got to find a way to improve your long-term win rate, and the only way to do that is to always place your bets on the highest expected value.