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Question

Difficulty: MediumSingle Event Probability

An aviation squadron has a total of 3030 crew members available for assignment. The squadron consists of 1212 pilots, 1010 mechanics, 55 medics, and 33 navigators. If one crew member is randomly selected to lead a safety briefing, what is the probability that the selected member is NOT a mechanic?

  1. 23\frac{2}{3}Answer
  2. B
    13\frac{1}{3}
  3. C
    12\frac{1}{2}
  4. D
    29\frac{2}{9}

Answer

The correct probability is 23\frac{2}{3}.
The correct answer is found by identifying the total number of crew members who are not mechanics (30−10=2030 - 10 = 20) and dividing this by the total number of crew members (3030). This forms the fraction 2030\frac{20}{30}, which simplifies to 23\frac{2}{3}.

Step-by-Step Solution

1
Identify the total number of possible outcomes.
Total crew members = 3030.
The denominator for a single event probability is the total population from which the selection is made.
2
Determine the number of favorable outcomes (crew members who are NOT mechanics).
30−10=2030 - 10 = 20 crew members.
The probability of a complementary event ('NOT' an event) can be found by subtracting the specific group from the total.
3
Calculate the probability as a ratio and simplify the fraction.
Probability = 2030=23\frac{20}{30} = \frac{2}{3}.
Probability is the number of favorable outcomes over the total outcomes, expressed in its simplest form.

Key Concept

Probability of a Complementary Event
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Topics

Single Event Probability

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