Theory question 105
ProbabilityThree school prefects are to be chosen from four girls and five boys. What is the probability that: (a) Only boys will be chosen; (b) more girls than boys will be chosen?
Show the model answer
Model answer
Total selections ⁹C₃ = 84.
(a) ⁵C₃ = 10, P = 10/84 = 5/42.
(b) 3 girls: ⁴C₃ = 4; 2 girls and 1 boy: ⁴C₂ × ⁵C₁ = 30. P = 34/84 = 17/42.
Explanation
Count favourable selections with combinations.