MHB Degrees of Vertices I: Is it Possible?

  • Thread starter Thread starter Joystar77
  • Start date Start date
  • Tags Tags
    Degrees
Click For Summary
In a graph with vertex set V = {v1, v2, v3, v4, v5}, the proposed degrees of the vertices are 3, 6, 2, 1, and 5. The calculation shows that 2E equals 17, leading to E being 8.5, which is not a whole number. Since the number of edges in a graph must be an integer, it is impossible for the vertices to have these specified degrees. Therefore, a graph with these vertex degrees cannot exist.
Joystar77
Messages
122
Reaction score
0
Let G be a graph with vertex set V = {v1, v2, v3, v4, v5}.

Is it possible for the degrees of the vertices to be 3, 6, 2, 1, 5, respectively? Why or why not?

2E = deg v1 + deg v2 + deg v3 + deg v4 + deg v5

2E = 3 + 6 + 2 + 1 + 5

2E = 17

E = 8.5

Is this correct to say that yes it is possible for the degrees of the vertices to be 3, 6, 2, 1, 5 because you end up with the number of edges being a decimal number?

Is it correct to say no that its not possible for the degrees of the vertices to be 3, 6, 2, 1, 5 because you end up with the number of edges being a decimal number?
 
Physics news on Phys.org
Joystar1977 said:
Let G be a graph with vertex set V = {v1, v2, v3, v4, v5}.

Is it possible for the degrees of the vertices to be 3, 6, 2, 1, 5, respectively? Why or why not?

2E = deg v1 + deg v2 + deg v3 + deg v4 + deg v5

2E = 3 + 6 + 2 + 1 + 5

2E = 17

E = 8.5

Is this correct to say that yes it is possible for the degrees of the vertices to be 3, 6, 2, 1, 5 because you end up with the number of edges being a decimal number?

Is it correct to say no that its not possible for the degrees of the vertices to be 3, 6, 2, 1, 5 because you end up with the number of edges being a decimal number?
The number of edges in a graph cannot be other than a whole number. Thus there is no graph possible which has vertices of degrees 3, 6, 2, 1, 5.
 
There is a nice little variation of the problem. The host says, after you have chosen the door, that you can change your guess, but to sweeten the deal, he says you can choose the two other doors, if you wish. This proposition is a no brainer, however before you are quick enough to accept it, the host opens one of the two doors and it is empty. In this version you really want to change your pick, but at the same time ask yourself is the host impartial and does that change anything. The host...

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
3
Views
2K
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
705
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K