## Thinking Mathematically (6th Edition)

See page 690, The Fundamental Counting Principle: 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. --------- Ways in which the 1st stock can change: 3 2nd stock can change: 3 ... 6th stock can change: 3 7th stock can change: 3 Total: $3\times 3\times...\times 3=3^{7}=2187$