# NCERT Class 8 Mathematics Solutions: Chapter 10 – Visualising Solid Shapes Exercise 10.3 Part 3

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Question 7: Using Euler’s formula, find the unknown:

Faces | ? | 5 | 20 |

Vertices | 6 | ? | 12 |

Edges | 12 | 9 | ? |

Answer:

In first column, F and

Using Euler’s formula, we see

Hence there are 8 faces.

In second column,

Using Euler’s formula, we see

Hence there are 6 vertices.

In third column,

Using Euler’s formula, we see

Hence there are 30 edges.

Question 8: Can a polyhedron have 10 faces, 20 edges and 15 vertices?

Answer:

If .

Then, we know Using Euler’s formula,

L.H.S

R.H.S = 2

.

Therefore, it does not follow Euler’s formula.