Chapter 12 - Data Analysis and Probability - 12-6 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 754: 12

a=6 and b=12

A) From A to B, there are 2 routes. From B to C, there are 3 routes. Multiply 2 and 3 to find the number of routes from A to B. 2$\times$6=6.So there are 6 routes from A to B. B)From A to B, there are 2 routes. From B to C, there are routes. From C to D, there are 2 routes. Multiply 2,3 and 2 to find the numbers of routes from A to D. 2$\times$ 3 $\times$2=12.So there are 12 routes from A to D.