Answer:
Option 1st is correct
number of vertices = 30
Step-by-step explanation:
Let e be the number of edges, f be the number of faces and v be the number of vertices.
As per the statement:
Number of edges(e) = 49
Number of faces(f) = 21
We have to find number of vertices.
using Euler's formula:
[tex]v-e+f = 2[/tex]
then;
[tex]v-49+21=2[/tex]
⇒[tex]v-28=2[/tex]
Add 28 to both sides we have;
[tex]v = 30[/tex]
Therefore, the number of vertices = 30
