[Math] Probablity of Being Chosen

probability

There are nine employess. Five are male, four are female. Three employees will be selected to go to a conference.

  1. How many possible combinations of three employees are possible?
  2. If each employee has equal chance of being selected for the trip, what is the probability that all three selected are males?

Best Answer

  1. Assuming order doesn't matter:

$\left( \begin{array}{c} 9 \\ 3 \end{array} \right) = \frac{9!}{6!\cdot3!}=\frac{9\cdot 8 \cdot 7}{3 \cdot 2 \cdot 1} = 3\cdot 4 \cdot 7 = 84$

  1. The probability that we get a male upon randomly selecting an employee: $\frac{5}{9}$. If we were to select another male, however, we'd have a $\frac{4}{8}$ chance. For a third male, it'd be $\frac{3}{7}$.

    Multiply the three probabilities together.