Chapter 7: Permutations and Combinations

Q1. Find 10P3.

Solution

10P3 = 10!/(10-3)! = 10 × 9 × 8 = 720

Q2. Find 12C4.

Solution

12C4 = 12!/(4!8!) = (12×11×10×9)/(4×3×2×1) = 495

Q3. In how many ways can 5 boys and 3 girls be seated alternately?

Solution

Arrange 5 boys: 5!
Place girls in gaps: 6P3
Total = 5! × 6P3 = 120 × 120 = 14400