Question: A professor is selecting 4 students at random from a group of 12 (7 math majors and 5 physics majors) to form a committee. What is the probability that the committee includes at least one math major and at least one physics major? - NBX Soluciones

Understanding the Context

Academic selection processes are more transparent than ever. As universities and project teams emphasize balanced, diverse inputs, variables like major background become subtle but significant factors. While not inherently complex, the math problem behind random student selection reflects broader challenges: how do we ensure inclusive representation without intentional bias?
This question surfaces in discussions about equity, randomness in group formation, and structured decision-making. As education shifts toward collaborative learning models, understanding these probabilities strengthens data literacy—helping students, educators, and professionals interpret random choices in committees, teams, and panels.

How to Calculate the Probability: Step by Step

To find the chance that at least one math major and one physics major are included in the 4-student committee, it’s easier to first calculate the opposite: the probability that the committee is entirely math or entirely physics. Then subtract from 1.

Total students: 12 (7 math, 5 physics)
Committee size: 4

Key Insights

Step 1: Total ways to choose 4 from 12
Use combinations:
[ \binom{12}{4} = \frac{12!}{4!(12-4)!} = 495 ]

Step 2: All-math committees
Only possible if 4 math majors are selected from 7:
[ \binom{7}{4} = 35 ]

Step 3: All-physics committees
Only possible if 4 physics majors are selected from 5:
[ \binom{5}{4} = 5 ]

Total ‘exclusive’ committees (all math or all physics):
[ 35 + 5 = 40 ]

Probability of all math or all physics:
[ \frac{40}{495} = \frac{8}{99} \approx 0.0808 ]

Final Thoughts

Probability of at least one from each group:
Subtract from 1:
[ 1 - \frac{8}{99} = \frac{