Ex 13.8 NCERT Solutions Class 9 Chapter 13
The solutions to exercise 13.8 (from class 9th's maths NCERT book) are given below. The exercise has 10 questions that have been explained thoroughly with proper reasoning.
Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 7 x 7 x 7
= 88/3 x 49
= 1437.33 cm 3
Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 0.63 x 0.63 x 0.63
= 4 x 22 x 0.09 x 0.21 x 0.63
= 1.048 cm 3
(i) the Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 14 x 14 x 14
= 88/3 x 2 x 14 x 14
= 11498.67 cm 3
(ii) Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 0.105 x 0.105 x 0.105
= 4 x 22 x 0.05 x 0.105 x 0.105
= 0.04851 cm 3
Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 2.1 x 2.1 x 2.1
= 4 x 22 x 0.1 x 2.1 x 2.1
= 38.808 cm 3
Mass of 1 cm 3 = 8.9 g
Mass of 38.808 cm 3 = 8.9 x 38.808
= 345.49 g
Diameter of moon
= ¼ the diameter of earth
If radius of earth is r
Radius of moon is r/4
Volume of moon : Volume of earth
4/3 x π (r/4) 3 : 4/3 x π r 3
(1/64) : 1
1: 64
Volume of hemispherical bowl
= 2/3 x π r 3
= ⅔ x 22/7 x 5.25 x 5.25 x 5.25
= 2 x 22 x 0.25 x 5.25 x 5.25
= 303.1875 cm 3
= 0.303 liters
= 2/3 x 22/7 ( 1.01 3 - 1 3)
= 0.06348
SA of sphere = 4 π r 2
154 = 4 x 22/7 x r 2
49/4 = r 2
7/2 = r
Volume of the sphere
= 4/3 x π r 3
= 4/3 x 22/7 x 3.5 x 3.5 x 3.5
= 179.66 cm3
Rs 2 is the cost of painting = 1 m2 area
Rs 498.96 is the cost of painting =
498.96/2 = 249.48 m2 area
CSA of hemisphere = 2 x 22/7 x r 2
249.48 =44/7 x r 2
39.69 = r 2
r= 6.3 m
Volume of the hemisphere:
= 2/3x 22/7 x r 3
= 2/3 x 22/7 x 6.3 x 6.3 x 6.3
= 44 x 0.3 x 6.3 x 6.3
= 523.908 m 3
r’ 3 = 27 x (r)3
r’ 3 = 3 3 x (r)3
r’ 3 = (3 r)3
r’ = 3 r
r’ 2 : r 2
r 2 : (3 r’) 2
r 2 : 9 r’ 2
1 : 9
Volume of the capsule
= 4/3x 22/7 x r3
= 4/3x (22/7) x 1.75 x 1.75 x 1.75
= 22.458 mm3
0 Comments