Question:

Four men and three women are standing in a line for railway ticket. The probability of standing them in alternate manner is

Updated On: Jun 20, 2022
  • $\frac{1}{35}$
  • $\frac{1}{33}$
  • $\frac{1}{84}$
  • $\frac{1}{7}$
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The Correct Option is A

Solution and Explanation

$\because$ Total outcomes $={ }^{7} P_{7}=7 !$
and favourable outcomes $=3 ! \times 4 !$
$\therefore$ Required probability $=\frac{\text { Favourable outcomes }}{\text { Total outcomes }}$
$=\frac{3 ! \times 4 !}{7 !}=\frac{3 \times 2 \times 1 \times 4 !}{7 \times 6 \times 5 \times 4 !}=\frac{1}{35}$
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Concepts Used:

Multiplication Theorem on Probability

In accordance with the multiplication rule of probability, the probability of happening of both the events A and B is equal to the product of the probability of B occurring and the conditional probability that event A happens given that event B occurs.

Let's assume, If A and B are dependent events, then the probability of both events occurring at the same time is given by:

\(P(A\cap B) = P(B).P(A|B)\)

Let's assume, If A and B are two independent events in an experiment, then the probability of both events occurring at the same time is given by:

\(P(A \cap B) = P(A).P(B)\)

Read More: Multiplication Theorem on Probability