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    NationalHardStatistics7–9

    Probability with Tree Diagrams

    Probabilidade com Diagramas em Árvore

    A bag contains 44 red and 66 blue balls. Two balls are drawn without replacement. Find the probability that both balls are red.

    The draws are without replacement, so the second probability is worked out from what is left in the bag after the first ball has been taken.

    Solution

    Step 1 of 4

    1. 1.P(both red)=P(1st red)×P(2nd red∣1st red)P(\text{both red}) = P(\text{1st red}) \times P(\text{2nd red} \mid \text{1st red})