a 2d triangle has 1 face known as a plane but a triangular prism has 4 faces
1 Face (2D) 4 Faces (3D) 3 Sides 3 Points, and 2 Congruent sides.
By its very nature of being a triangle, and a 2D shape, a triangle cannot have four plane faces. However, a tetrahedron is a polyhedron made up of four triangular faces.
all 2D figures have 1 face.
One.
One
trianle have no faces, because it is 2D figure.
a 2d triangle has 1 face known as a plane but a triangular prism has 4 faces
1 for a 2d and triangular pyramid-5 
Only one; a triangle is a 2D shape, not a 3D shape. Usually only 3D (or more) shapes are considered to have 'faces'.
1 Face (2D) 4 Faces (3D) 3 Sides 3 Points, and 2 Congruent sides.
4
By its very nature of being a triangle, and a 2D shape, a triangle cannot have four plane faces. However, a tetrahedron is a polyhedron made up of four triangular faces.
all 2D figures have 1 face.
no stupid because one has got faces(3d) and the other has sides(2d)
One.
it can have 1 if it is a right triangle.