Question

Use Euler’s Formula to find the missing number.

Answer 1

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:

$v-e+f = 2$

then;

$v-49+21=2$

⇒$v-28=2$

Add 28 to both sides we have;

$v = 30$

Therefore, the number of vertices = 30

Answer 2

It is 30, 30 - 49 is -19 plus 21 is 2