Explanation
Yes, a polyhedra with exactly 4 triangular faces can exist,
A polyhedra with 4 triangular faces is triangular Pyramid.
No, a polyhedron with 3 triangular faces does not exist,
Because For polyhedrons to exist they must have 4 triangular faces.
Given: No. of face(F):10
No. of edges(E):20
No. of vertices(V):15
According to Euler formula, we know that
F + V = E + 2
That is, here
10 + 15 = 20 + 2
⇒ 25 = 22
This is not true.(That is, 25≠22 )
∴ A polyhedra with 10 faces, 20 edges and 15 vertices is not possible.
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