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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Probability

NDA 2025 · Mathematics · Probability

Consider the following for the two (02) items that follow: The...

Consider the following for the two (02) items that follow:
The probabilities that AA, BB and CC become managers are 310\dfrac{3}{10}, 12\dfrac{1}{2} and 45\dfrac{4}{5} respectively. The probabilities that bonus scheme will be introduced if AA, BB and CC become managers are 49\dfrac{4}{9}, 29\dfrac{2}{9} and 13\dfrac{1}{3} respectively.

What is the probability that the bonus scheme will be introduced?

Options

  1. A1745\dfrac{17}{45}
  2. B1945\dfrac{19}{45}
  3. C2345\dfrac{23}{45}
  4. D2645\dfrac{26}{45}

Correct answer

C. 2345\dfrac{23}{45}

Step-by-step solution

Let E1E_1, E2E_2, and E3E_3 be the events that AA, BB, and CC become managers respectively.

The given probabilities are:
P(E1)=310P(E_1) = \dfrac{3}{10}
P(E2)=12P(E_2) = \dfrac{1}{2}
P(E3)=45P(E_3) = \dfrac{4}{5}

Let SS be the event that the bonus scheme is introduced. The conditional probabilities are:
P(S∣E1)=49P(S|E_1) = \dfrac{4}{9}
P(S∣E2)=29P(S|E_2) = \dfrac{2}{9}
P(S∣E3)=13P(S|E_3) = \dfrac{1}{3}

Using the law of total probability, the probability that the bonus scheme will be introduced is:
P(S)=P(E1)P(S∣E1)+P(E2)P(S∣E2)+P(E3)P(S∣E3)P(S) = P(E_1)P(S|E_1) + P(E_2)P(S|E_2) + P(E_3)P(S|E_3)

Substituting the given values:
P(S)=P(S) =\left(\dfrac{3}{10} \times \dfrac{4}{9}\right) + (12×29)+(45×13)<br><br>\left(\dfrac{1}{2} \times \dfrac{2}{9}\right) + \left(\dfrac{4}{5} \times \dfrac{1}{3}\right)<br><br>P(S) = 1290+218+415<br><br>\dfrac{12}{90} + \dfrac{2}{18} + \dfrac{4}{15}<br><br> P(S) = 215+19+415<br><br>\dfrac{2}{15} + \dfrac{1}{9} + \dfrac{4}{15}<br><br> P(S) = 615+19<br><br>\dfrac{6}{15} + \dfrac{1}{9}<br><br> P(S) = 25+19<br><br>\dfrac{2}{5} + \dfrac{1}{9}<br><br> P(S) = 18+545=2345\dfrac{18 + 5}{45} = \dfrac{23}{45}<br><br>Answer:<br><br>Answer:2345\dfrac{23}{45}
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