probability problems Practice Question and Answer

Q:

A school has 45% girls. If 80% of girls score more than 75% marks and 70% of the boys have score more than 75% marks. If a student is selected at random and is found to have more than 75% marks, find the probability of it being a boy.

374 0

  • 1
    77/149
    Correct
    Wrong
  • 2
    75/149
    Correct
    Wrong
  • 3
    Cannot be determined
    Correct
    Wrong
  • 4
    11/20
    Correct
    Wrong
  • 5
    9/20
    Correct
    Wrong
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Answer : 1. "77/149"

Q:

A person can hit a target 5 times out of 8 shots. If he fires 10 shots, what is the probability that he will the target twice?

761 0

  • 1
    $${1135×3^8}\over 8^{10} $$
    Correct
    Wrong
  • 2
    $${1165×3^8}\over 8^{10} $$
    Correct
    Wrong
  • 3
    $${1175×3^8}\over 8^{10} $$
    Correct
    Wrong
  • 4
    $${1125×3^8}\over 8^{10} $$
    Correct
    Wrong
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Answer : 4. " $${1125×3^8}\over 8^{10} $$"

Q:

A speaks the truth 5 out of 7 times and B speaks truth 8 out of 9 times. What is the probability that they contradict each other in stating the same fact?

646 0

  • 1
    $${1\over 7}$$
    Correct
    Wrong
  • 2
    $${1\over 9}$$
    Correct
    Wrong
  • 3
    $${1\over 4}$$
    Correct
    Wrong
  • 4
    $${1\over 3}$$
    Correct
    Wrong
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Answer : 4. "$${1\over 3}$$"

Q:

The probabilities of solving a problem by three students A, B and C are  $$3\over 7$$, $$5\over 9$$ and $$1\over 5$$ respectively. The probability that problem will be solved is:

424 0

  • 1
    $$155\over 315$$
    Correct
    Wrong
  • 2
    $$64\over 315$$
    Correct
    Wrong
  • 3
    $$251\over 315$$
    Correct
    Wrong
  • 4
    $$32\over 315$$
    Correct
    Wrong
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Answer : 3. "$$251\over 315$$"

Q:

In a box there are 6 blue ball, X red balls & 10 green balls. Probability of choosing one red ball from the given box is $$ {1\over 3}$$. Then find the sum of red and blue balls in the box?

860 0

  • 1
    20
    Correct
    Wrong
  • 2
    12
    Correct
    Wrong
  • 3
    14
    Correct
    Wrong
  • 4
    18
    Correct
    Wrong
  • 5
    16
    Correct
    Wrong
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Answer : 3. "14"

Q:

A box contains 10 red ball, 6 green ball if 2 balls are drawn randomly what is the probability of getting non-green ball?

1026 0

  • 1
    $${5\over16}$$
    Correct
    Wrong
  • 2
    $${16\over55}$$
    Correct
    Wrong
  • 3
    $${3\over8}$$
    Correct
    Wrong
  • 4
    $${5\over8}$$
    Correct
    Wrong
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Answer : 3. "$${3\over8}$$ "

Q:

A bag contains 3 white balls and 2 black balls. Another bag contains 2 white and 4 black balls. A bag and a ball are picked random. The probability that the ball will be white is:

901 0

  • 1
    7/15
    Correct
    Wrong
  • 2
    9/16
    Correct
    Wrong
  • 3
    4/15
    Correct
    Wrong
  • 4
    3/5
    Correct
    Wrong
  • 5
    8/5
    Correct
    Wrong
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Answer : 4. "3/5 "

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