RS Aggarwal solution class 8 chapter 19 Three Dimensional Figure Exercise 19A

Exercise 19A

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Q1 | Ex-19A | Class 8 | RS AGGARWAL | chapter 19 | Three Dimensional Figure

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Question 1:

Write down the number of faces of each of the following figures:
(i) Cuboid
(ii) Cube
(iii) Triangular prism
(iv) Square pyramid
(v) Tetrahedron

Answer 1:

(i) A cuboid has 6 faces, namely ABCD, EFGH, HDAE, GCBF, HDCG and EABF.

(ii) A cube has 6 faces, namely IJKL, MNOP, PLIM, OKJN, LKOP and IJNM.

(iii) A triangular prism has 5 faces (3 rectangular faces and 2 triangular faces), namely  QRUT, QTVS, RUVS, QRS and TUV.

(iv) A square pyramid has 5 faces (4 triangular faces and 1 square face), namely OWZ, OWX, OXY, OYZ and WXYZ.

(v) A tetrahedron has 4 triangular faces, namely KLM, KLN, LMN and KMN.

Q2 | Ex-19A | Class 8 | RS AGGARWAL | chapter 19 | Three Dimensional Figure

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Question 2:

Write down the number of edges of each of the following figures:
(i) Tetrahedron
(ii) Rectangular pyramid
(iii) cube
(iv) Triangular prism

Answer 2:

(i) A tetrahedron has 6 edges, namely KL, LM, LN, MN, KN and KM.

(ii) A rectangular pyramid has 8 edges, namely AB, AE, AD, AC, EB, ED, DC and CB.

(iii)  A cube has 12 edges, namely PL, LK, KO, OP, MN, NJ, JI, IM, PM, LI, ON and KJ.

(iv) A triangular prism has 9 edges, namely QR, RS, QS, TU, TV, UV, QT, RU, and SV.

Q3 | Ex-19A | Class 8 | RS AGGARWAL | chapter 19 | Three Dimensional Figure

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Question 3:

Write down the number of vertices of each of the following figures:
(i) Cuboid
(ii) Square pyramid
(iii) Tetrahedron
(iv) Triangular prism

Answer 3:

(i) A cuboid has 8 vertices, namely A, B, C, D, E, F, G and H.

(ii) A square pyramid has 5 vertices, namely O, W, X, Y and Z.



(iii) A tertrahedron has 4 vertices, namely K, L, M and N.


(iv) A triangular prism has 6 vertices, namely Q, R, S, T, U and V.

Q4 | Ex-19A | Class 8 | RS AGGARWAL | chapter 19 | Three Dimensional Figure

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Question 4:

Fill in the blanks:
(i) A cube has ....... vertices, ....... edges and ....... faces.
(ii) The point at which three faces of a figure meet is known as its .......
(iii) A cuboid is also known as a rectangular .......
(iv) A triangular pyramid is called a .......

Answer 4:

(i) A cube has 8 vertices, 12 edges and 6 faces.                   
Vertices: I, J, K, L, M, N, O and P
Edges : IJ, JN, NM, MI, PL, LK, KO, OP, PM, LI, KJ, and ON
Faces : MNJI, POKL, PLIM, OKJN, PONM and LKJI


(ii) The point at which the three faces of a figure meet is known as its vertex.
(iii) A cuboid is also known as a rectangular cube.
(iv) A triangular pyramid is called a tetrahedraon.