Question

Look at the net of the polyhedron shown below.

A net is shown. It has two pentagons joined by a square in the middle. The square in the middle is joined to two other squares on the left and two more rectangles on the right.

The number of vertices of the polyhedron is ________.

Answer 1

The answer is 13

Euler's formula:
F + V - E = 2
F - number of faces
V - number of vertices
E - number of edges

We have:
F = 7
V = ?
E = 18

7 + V - 18 = 2
7 + V = 2 + 18
7 + V = 20
V = 20 - 7
V = 13