Question 1
In how many ways can 8 people be arranged in a row if a specific person must be at the first position?
Step-by-Step Solution:
Concept: Permutation with fixed position constraint.
Strategy: Fix the restricted position, then arrange remaining elements.
Given:
- Total people: 8
- Constraint: One specific person must be first
Step 1 - Fix First Position:
First position has only 1 choice (the specific person)
Step 2 - Arrange Remaining:
Remaining 7 people can be arranged in 7! ways
Calculation:
Total arrangements = 1 × 7!
= 5040
= 5040
Alternative Approach:
Total arrangements without restriction = 8! = 40320
Fraction with specific person first = 40320 / 8 = 5040
Key Principle: Fixing one position reduces the problem to arranging (n-1) elements.
Concept: Permutation with fixed position constraint.
Strategy: Fix the restricted position, then arrange remaining elements.
Given:
- Total people: 8
- Constraint: One specific person must be first
Step 1 - Fix First Position:
First position has only 1 choice (the specific person)
Step 2 - Arrange Remaining:
Remaining 7 people can be arranged in 7! ways
Calculation:
Total arrangements = 1 × 7!
= 5040
= 5040
Alternative Approach:
Total arrangements without restriction = 8! = 40320
Fraction with specific person first = 40320 / 8 = 5040
Key Principle: Fixing one position reduces the problem to arranging (n-1) elements.