Permutations & Combinations
Fundamental Principle of Counting
Grade 11
Question:
<p>There are 25 students in a class in which 15 boys and 10 girls. The class teacher selects either a boy or a girl for monitor of the class. In how many ways can the class teacher make this selection?</p>
Step-by-Step Solution
Key Concept: Use the addition principle when events are mutually exclusive (either one or the other, but not both can occur simultaneously).
<p><strong>Step 1:</strong> There are 15 ways to select a boy for monitor.</p><p><strong>Step 2:</strong> There are 10 ways to select a girl for monitor.</p><p><strong>Step 3:</strong> Since the teacher must select either a boy or a girl (mutually exclusive events), by the Fundamental Principle of Addition, the total number of ways = 15 + 10 = 25 ways.</p>
Correct Answer: 25