## Thinking Mathematically (6th Edition)

The number of ways in which a series of successive things can occur is found by multiplying the number of ways in which each thing can occur. ---------- 1. The path from A to B can be chosen in 3 ways. 2. The path from B to C can be chosen in 2 ways. 3. The path from C to D can be chosen in 4 ways. Applying the Principle, the total number of routes from A to D is 3$\times$2$\times$4$=24$