Twenty edges
If it lies in a plane, it is a decagon.
it is a decagon
A decagon has 10 angles (and sides)
A vertex is the same as an angle. A decagon has 10.A vertex is the same as an angle. A decagon has 10.A vertex is the same as an angle. A decagon has 10.A vertex is the same as an angle. A decagon has 10.
1 face 10 edges
10 sides and 10 angles
A regular decagon
decagon
Assuming a regular decagon is the base of the prism, it would be 10 faces. With an irregular decagon, it is possible that two (or more) of the edges of the decagons are perpendicular, so all 12 faces could have perpendicular edges.
a nonagon a shape with nine edges is called a nonagon. just like pentagon and decagon a shape with nine edges is called a nonagon. just like pentagon and decagon
A decagon is a shape that has ten edges. DEC means TEN.
Twenty edges
If it lies in a plane, it is a decagon.
Not sure what a decagonal is. Since the question refers to faces, edges and vertices, it may be assumed that the object in question is 3-dimensional. A decagon certainly is not, so decagonal cannot be a mistaken name for a decagon.
it is a decagon
12 faces, 30 edges and 20 vertices. It has 2 decagons plus 10 rectangles between them giving 12 faces It has 2 x 10 vertices on each decagon giving 20 vertices It has 10 edges round each decagon plus another 10 joining the vertices of one decagon to the other decagon's vertices giving 2x10+10 = 30 vertices