(i) Number of faces = F = 7
Number of vertices = V = 10
Number of edges = E = 15
We have, F + V − E = 7 + 10 − 15 = 17 − 15 = 2
Hence, Euler’s formula is verified.
(ii) Number of faces = F = 9
Number of vertices = V = 9
Number of edges = E = 16
F + V − E = 9 + 9 − 16 = 18 − 16 = 2
Hence, Euler’s formula is verified.