Question of Probability

My friend Parveen teaches at a school. One day she conducted a test for three of her students and when they handed back the test papers, they had forgotten to write their names.

Parveen returned the papers to students at random.

What is probability that none of three students will get the right paper?

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Vineet Patawari

Hi, I'm Vineet Patawari. I fell in love with numbers after being scared of them for quite some time. Now, I'm here to make you feel comfortable with numbers and help you get rid of Math Phobia!

9 thoughts to “Question of Probability”

  1. 3 students so 3 papers so possibility of
    1. correct and
    2. not correct are the possibilities for given scenarios in question.

    now: 2 type of possibilities per student, hence 2 ^ 3 = 8 possibilities for total 3 students

    hence our N = 8
    now favorable case is – 0 for none of total students get correct answer sheet back

    I would do this based on a shortcut key:

    11 ^ 3 = 1 3 3 1
    ———————————–
    positions 0 1 2 3 — favorable events

    for given scenario, favorable even makes as 0 so its related digit is -> 1

    hence….

    1/N = 1/ 8

    answer will be 1/8 for given question above.

  2. 2/3 that first student gets wrong paper
    1/2 that second student gets wrong paper ( assuming first gets wrong paper )
    1 that third student gets wrong paper ( assuming first and second get wrong paper )

    So probability = 2/3 * 1/2 * 1 = 1/3

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