Write down the Euler's formula and verify the following.

Regular octahedron

If a polyhedron has $30$ edges and $20$ vertices, how many faces does it have?

Calculate the following.

If a polyhedron has $24$ edges and $10$ faces, how many vertices does it have?

If a polyhedron has $10$ faces and $7$ vertices, how many edges does it have?

Look at the following figures and verify Euler's formula, where $F, V$ and $E$ stand for number of faces, number of vertices and number of edges respectively.

Look at the following figures and verify Euler's formula, where $F, V$ and $E$ stand for number of faces, number of vertices and number of edges respectively.

Look at the following figures and verify Euler's formula, where $F, V$ and $E$ stand for number of faces, number of vertices and number of edges respectively.

Look at the following figures and verify Euler's formula, where $F, V$ and $E$ stand for number of faces, number of vertices and number of edges respectively.

Look at the following figures and verify Euler's formula, where $F, V$ and $E$ stand for number of faces, number of vertices and number of edges respectively.