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You are here: Home / ACT Released Tests / Video Explanations: 2017 December ACT (A10/75E)

Video Explanations: 2017 December ACT (A10/75E)

2017 December ACT (A10/75E): Answers

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This test is identical to the Practice Test 5 (Form 19MC5) in The Official ACT Prep Guide 2019-20 released in May 2019.

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Comments

  1. Prabh Dhaliwal says

    February 5, 2019 at 8:53 PM

    I understand that when doing probability that A or B occurs you add probabilities but in some scenarios you must subtract the probably that both A and B occur from the sum. Which scenarios does this apply to.

    P(AUB)= P(A) + P(B) – P(A and B)

    Reply
    • Dabral says

      February 6, 2019 at 9:37 PM

      When events A and B are mutually exclusive, meaning events that cannot occur at the same time, we have P(A and B)=0. For example, if a 6-sided die is rolled once, the event of rolling an odd number and the event of rolling an even number are mutually exclusive. In this case, the formula reduces to P(A or B, or both, occur) = P(A) + P(B). But you are right that in the general case P(A or B, or both, occur) = P(A) + P(B) – P(both A and B occur), which then reduces to the sum of the probabilities of the two events when they are mutually exclusive.

      Reply

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