From a group of 10 boys and 12 girls, a committee of 4 students is chosen at random. a. What is the probability that all 4 members on the committee will be girls? b. What is the probability that all 4 members of the committee will be boys? c. What is the probability that there will be at least 1 girl on the committee?
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To find the probabilities, we'll start by calculating the total number of ways to choose a committee of 4 students from a group of 10 boys and 12 girls, which makes a total of 22 students. The total ways to choose 4 students from 22 is calculated using the combination formula \( C(n, k) \), which is given by: \[ C(n, k) = \frac{n!}{k!(n-k)!} \] where \( n \) is the total number of items, \( k \) is the number of items to choose, and \( ! \) denotes factorial. 1. **Total combinations \( C(22, 4) \)**: \[ C(22, 4) = \frac{22!}{4!(22-4)!} = \frac{22 \times 21 \times 20 \times 19}{4 \times 3 \times 2 \times 1} = 7315 \] a. **Probability that all 4 members on the committee will be girls**: To find the number of combinations of 4 girls from 12: \[ C(12, 4) = \frac{12!}{4!(12-4)!} = \frac{12 \times 11 \times 10 \times 9}{4 \times 3 \times 2 \times 1} = 495 \] The probability is then given by: \[ P(\text{all girls}) = \frac{C(12, 4)}{C(22, 4)} = \frac{495}{7315} \approx 0.0677 \] b. **Probability that all 4 members of the committee will be boys**: To find the number of combinations of 4 boys from 10: \[ C(10, 4) = \frac{10!}{4!(10-4)!} = \frac{10 \times 9 \times 8 \times 7}{4 \times 3 \times 2 \times 1} = 210 \] The probability is then given by: \[ P(\text{all boys}) = \frac{C(10, 4)}{C(22, 4)} = \frac{210}{7315} \approx 0.0287 \] c. **Probability that there will be at least 1 girl on the committee**: To find this, it's easier to use the complement rule. The probability that there are at least 1 girl can be calculated as: \[ P(\text{at least 1 girl}) = 1 - P(\text{all boys}) = 1 - \frac{210}{7315} = 1 - 0.0287 \approx 0.9713 \] So, the final probabilities are approximately: - a. 0.0677 (probability all girls) - b. 0.0287 (probability all boys) - c. 0.9713 (probability at least 1 girl)