RS Aggarwal Class 8 Math Nineteenth Chapter Three-Dimensional Figures Exercise 19B Solution
EXERCISE 19B
(1) Define Euler’s relation between the number of faces, number of edges and number of vertices for various 3-dimensional figures.
Ans: In a 3-dimensional figure, let the number of faces be F; the number of edges be E and the number of vertices be V.
Then, the Euler’s relation is given by
F – E + V = 2
(2) How many edges are there in a
(i) Cuboid = 12 edges
(ii) Tetrahedron = 6 edges
(iii) Triangular prism = 9 edges
(iv) Square pyramid = 8 edges
(3) How many faces are there in a
(i) Cube = 6 faces
(ii) Pentagonal prism = 7 faces
(iii) Tetrahedron = 4 faces
(iv) Pentagonal pyramid = 6 faces
(4) How many vertices are there in a
(i) Cuboid = 8 vertices
(ii) Tetrahedron = 4 vertices
(iii) A triangular prism = 10 vertices
(iv) A square pyramid = 5 vertices