00:01
In this problem they want to know the number of vertices and edges in each of these diagrams.
00:06
So in this first one we can see that we have vertices one.
00:11
Let's start with a, b, c, d, four vertices.
00:16
And edges we got, we have to count these lines.
00:19
These are what we call edges.
00:20
So we got one to three on here on top.
00:23
Then one here, that's four, five, six, seven, eight.
00:29
So we got eight.
00:30
Edges.
00:35
On this one, the vertices are a, b, c, d, e.
00:38
We got five vertices.
00:41
So the vertices are five, and the edges are one, two, three, four, five, six, seven, eight, nine, ten.
00:54
These ones are already counted and eleven.
00:58
So, twelve and thirteen.
01:02
Let's recount just to make sure that we got all of them.
01:05
13 seems to be the number, we'll write it down and we'll come to them again.
01:11
So we got one, two, three, four, five, six.
01:15
So we got, here we got two, four, here we got three, here we got three.
01:22
So that's ten in total, eleven, twelve, thirteen.
01:27
So thirteen is the right number.
01:31
Then they ask what is the in degree and out degree of each vertex? that's simply how many of these edges go in and how many go out.
01:44
So we compute that for each one.
01:46
Let's start with this one.
01:47
We have, let's start by in first.
01:50
We're going to write the in first and the out...