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Probability and Conditional Probability Flashcards

7 cards from real Bluebook SAT Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Probability and Conditional Probability flashcards as text

  1. A class has 24 students. The probability of any student being absent on a given day is 0.05. What is the expected number of absent students?

    Answer: 1.2

    E = n × p = 24 × 0.05 = 1.2.

  2. The two-way table shows 200 voters by party and stance on a bill. Favor Oppose Democrat 70 30 Republican 20 80 Given that a voter favors the bill, what is the probability the voter is a Republican?

    Answer: 2/9

    Total favoring = 70 + 20 = 90; Republicans favoring = 20; P = 20/90 = 2/9.

  3. Cards numbered 1 through 20 are shuffled. One card is drawn at random. What is the probability the card shows a multiple of 3 or a multiple of 5?

    Answer: 2/5

    Multiples of 3: {3,6,9,12,15,18} = 6; multiples of 5: {5,10,15,20} = 4; overlap {15} = 1; union = 9; P = 9/20.

  4. A bag has 5 red and 5 blue chips. Two chips are drawn without replacement. What is the probability both are the same color?

    Answer: 4/9

    P(RR) = (5/10)(4/9) = 20/90; P(BB) = (5/10)(4/9) = 20/90; total = 40/90 = 4/9.

  5. A company's hiring data shows: 40% of applicants pass the written test and, of those, 30% pass the interview. What percent of all applicants get hired?

    Answer: 12%

    P(pass written and interview) = 0.40 × 0.30 = 0.12 = 12%.

  6. The two-way table shows 300 students by study method and test result. Pass Fail Study group 110 40 Study alone 90 60 What is the probability a student who failed studied alone?

    Answer: 3/5

    Total failing = 40 + 60 = 100; studied alone and failed = 60; P = 60/100 = 3/5.

  7. A number is selected at random from 1 to 50. What is the probability it is divisible by both 4 and 6?

    Answer: 2/25

    LCM(4,6) = 12; multiples of 12 up to 50: {12, 24, 36, 48} = 4; P = 4/50 = 2/25.