Graph theory

[thorny ginkgo]

Hello! How many ways between A and B ?

[near silo]

I'm an absolute noob, but if you sum up the possibilities for each outgoing edge it should work - i got 25

[sharp robin]

Denote by A,B,C,D,E,F,G,H,I the number of ways to each corresponding vertex from A. Moving from B backwards you can express each number as a sum of the number of ways to the neighboring vertices. For example you can get to B only from H and I. So, the number of ways from A to B equals the number of ways from A to H plus the number of ways from A to I. Thus B=H+I. And so on, you make equations moving backwards. You get a system of equations, which is easy to solve. Finally, B=16.

[thorny ginkgo]

It’s false

Are u sure @sharp robin

[sharp robin]

why?

[thorny ginkgo]

F = 1
E = 3
D = 4
A = 1 right?

[sharp robin]

nope, A=1

[thorny ginkgo]

Yeah 1 sorry

Are u sure it’s 16

[sharp robin]

Do my 'yes' or ''no'' change anything? It's math. If you understand the solution and see no logical mistake then it is correct. If you see a mistake name it.

[sharp robin]

by the way, I found a mistake 🙂

In that system D=A+E, because we get into D from A and E, not only A.

So, this is a correct version