Flip the thing you’re looking at – instead of a 70% vs 7%x10, look at 30% vs 93%x10. In the first case, there’s a 30% chance of losing. In the second, you have a 93% chance to lose, then a 93% chance on the next one, etc. Since you’re only interested in cases where you lose every single time (because otherwise you’ll have succeeded at least once) you can multiply the chances. So what’s 93% * 93% * 93%…etc? A bit higher than 48%. So the first option has only a 30% chance of losing while the second one has a 48% chance of losing overall.
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