PYQ Vault

Given P(A given B), P(B given A) and P(A and B): find other probabilities

This type of question, asked 3 times: 25 Jun 2022, 28 Jul 2022, 22 Jan 2025. All 3 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    25 Jun 2022

    70
    Let E1E_{1} and E2E_{2} be two events such that the conditional probabilities P(E1∣E2)=12P\left( E_{1}\mid E_{2} \right)=\frac{1}{2}, P(E2∣E1)=34P\left( E_{2}\mid E_{1} \right)=\frac{3}{4} and P(E1∩E2)=18P\left( E_{1}\cap E_{2} \right)=\frac{1}{8}. Then:

    Tap an option to check your answer.

  2. Question 2

    28 Jul 2022

    169
    Let AA and BB be two events such that P(B∣A)=25P(B \mid A) =\frac{2}{5}, P(A∣B)=17P(A \mid B) =\frac{1}{7} and P(A∩B)=19P(A \cap B) =\frac{1}{9}. Consider (S1)P(A′∪B)=56(S1)P\left( A^{'}\cup B \right)=\frac{5}{6}, (S2) P(A′∩B′)=118P\left( A^{'}\cap B^{'} \right)=\frac{1}{18}. Then

    Tap an option to check your answer.

  3. Question 3

    22 Jan 2025

    142
    If AA and BB are two events such that P(A∩B)=0.1P(A \cap B) = 0.1, and P(A∣B)P(A \mid B) and P(B∣A)P(B \mid A) are the roots of the equation 12x2−7x+1=012x^{2}- 7x + 1 = 0, then the value of P(A‾∪B‾)P(A‾∩B‾)\frac{P(\overline{A}\cup\overline{B})}{P(\overline{A}\cap\overline{B})} is:

    Tap an option to check your answer.