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Color Balls

CalcMedium~15 min· Probability
Problem

The Problem

An urn contains 5 red, 3 green, and 2 blue balls. You draw balls one at a time without replacement until the urn is empty.

  1. What is the probability that all 5 red balls come out consecutively (as a single block of 5 reds in a row)?
  2. What is the probability that no two adjacent balls in the draw sequence have the same color?
  3. What is the expected number of color changes (adjacent pairs with different colors) in the sequence?