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In Ms. Smith's class, each student averages one day absent out of thirty. What is the probability that out of any two students chosen at random, one student will be absent while the other is present? Express your answer as a percent rounded to the nearest tenth.

thanks!

 May 25, 2020
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Let the two students chosen are A and B

P(A is absent) = P(A) = 1/30

P(Ac) = 1-1/30 = 29/30

P(B is absent) = P(B) = 1/30

P(Bc) = 1-1/30 = 29/30

Required probability = P(ABc or AcB)

= P(A)*P(Bc) + P(Ac)*P(B)

= 1/30*29/30 + 29/30*1/30

= 29/900 + 29/900

= 58/900

= 0.0644 or 6.44%

 Feb 5, 2021

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