Hi. The question is:

A, B, C, and D are nodes on a computer network. There are two paths between A and C, two between B and D, three between A and B and four between C and D. Along how many routes can a message from A to D be sent?

My thinking:
I came up with two ways a message can go from A to D.

A to C, C to D --> 2 + 4 --> 6 paths
A to B, B to D --> 3 + 2 --> 5 paths

Do I use the addition or multiplication principle for this problem?

Thanks!

1 answer

A to C ,C to D ==> (2)x(4)ways=8 ways
A to B ,B to D = 3x2 =6 ways
Since both events are mutually exclusive then we using sum rule= 8 + 6 =14