The Blue-Cab Problem

Level 2●●●○○ Medium~5 min

Problem

A city's cabs are

85\%

Green and

15\%

Blue. A witness to a night-time hit-and-run identifies the cab as Blue. Under court-tested conditions the witness correctly identifies a cab's colour

80\%

of the time (for both colours). What is the probability the cab was actually Blue?

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