Brain Teasers & Mental Math
Expected value: a game costs $10 to play. You roll one fair die and win $3 times the number shown. Should you play?
Model answer
Yes — it has positive expected value.
Expected face value = (1+2+3+4+5+6)/6 = 3.5. Expected payout = $3 × 3.5 = $10.50. Cost is $10, so expected net = +$0.50 per play. Positive EV…
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