In an octahedron; number of faces is :

1. half of the number of edges

2. 8

3. 12

4. more than the number of edges

A rectangular pyramid has :

1. 4 vertices and 4 faces

2. 6 vertices and 6 faces

3. 7 vertices and 4 faces

4. 5 vertices and 5 faces

If V stands for number of vertices, F stands for number of faces and E stands for number of edges, then :

1. V + F + E = 2

2. F + E - V - 2 = 0

3. F + V - E = 2

4. F - E + V + 2 = 0

If in a polyhedron, number of faces = 12 and number of vertices is 20, then the number of edges is :

1. 10

2. 20

3. 30

4. 40