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Posted by on Thursday, November 5, 2009 at 11:04pm.

Mary's class took two tests last week. 80% of the class passed the math test, 90% of the class passed the English test, and 72% of the class passed both. What is the probablility that a randomly selected student in Mary's class failed both tests? Express your answer as a percent rounded to the nearest tenth of a percent?
Thanks
-Zach

  • Algebra 1 - , Thursday, November 5, 2009 at 11:11pm

    Prob(Math OR English)
    = P(M) + P(E) - P(M and E)
    = .8 + .9 - .72
    = .98

    Prob (failing both) = 1 - .98
    = .02

  • Algebra 1 - , Thursday, November 5, 2009 at 11:26pm

    Thanks

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