Statistics - Probability

Question

Suppose a jar contains 17 red marbles and 37 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.

  

Answer 1

Because you're pulling out marbles without replacement (marbles are coming out of the jar at the same time), we'll use combinations to solve for this.

Number of ways I can select 2 red marbles: ₁₇C₂ = 136

Number of ways I can select 2 marbles: ₅₄C₂ = 1431

Probability of selecting 2 red marbles: 136/1431 ≈ 9.504%