Volume and Surface Area of Solid Figures
- The volumes of a sphere and a right circular cylinder having the same radius are equal. The ratio of the diameter of the sphere to the height of the cylinder is ?
-
View Hint View Answer Discuss in Forum
Let r = Radius of cylinder = Radius of sphere, h = Height of the cylinder.
According to the question.
4/3πr3 = πr2hCorrect Option: D
Let r = Radius of cylinder = Radius of sphere, h = Height of the cylinder.
According to the question.
4/3πr3 = πr2h
⇒ h = 4r/3
⇒ 4r = 3h
⇒ 2r = 3/2h
⇒ 2r/h = 3/2
∴ Required ration = 3 : 2
- How many spherical bullets can be made out of a solid cube whose edge measures 44 cm, each bullet being 4 cm in diameter ?
-
View Hint View Answer Discuss in Forum
Volume of 1 bullet = 4/3π(2)3 = (32/3 x 22/7) cm3
Volume of the cube = (44)3Correct Option: B
Volume of 1 bullet = 4/3π(2)3 = (32/3 x 22/7) cm3
Volume of the cube = (44)3
∴ Number of bullets = Volume of solid/Volume of 1 bullet
= (44)3 x 3 x 7 / 32 x 22 = 2541
- A hemisphere has 28 cm diameter. Find its curved surface area. ?
-
View Hint View Answer Discuss in Forum
Curved surface area = 2πr2
Correct Option: A
Curved surface area = 2πr2
= 2π x 14 x 14 = 2 x (22/7) x 14 x 14
= 2 x 22 x 2 x 14
= 88 x 14
= 1232 sq cm
- If the ratio of the diameters of two spheres is 3: 5, then what is the ratio of their surface areas ?
-
View Hint View Answer Discuss in Forum
Let the diameter's of two sphere are d1 and d2, respectively.
∴ Ratio of their surface areas = 4πr12/4πr22Correct Option: A
Let the diameter's of two sphere are d1 and d2, respectively.
∴ Ratio of their surface areas = 4πr12/4πr22
= (2r1)2/(2r2)2 = d12/d22
= (d1/d2)2 = (3/5)2 = 9/25 = 9 : 25
- If 64 identical small spheres are made out of a big sphere of diameter 8 cm, what is surface area of each small sphere ?
-
View Hint View Answer Discuss in Forum
Volume of small spheres
= Volume of bigger sphere / Number of small spheres = [(4/3)π(4)3] / 64
= [(4/3) x π x 4 x 4 x 4] / 64
= 4/3 π cm3
Let radius of small sphere be r
∴ 4/3πr3 = 4π/3
⇒ r2 = 1 cmCorrect Option: C
Volume of small spheres
= Volume of bigger sphere / Number of small spheres = [(4/3)π(4)3] / 64
= [(4/3) x π x 4 x 4 x 4] / 64
= 4/3 π cm3
Let radius of small sphere be r
∴ 4/3πr3 = 4π/3
⇒ r2 = 1 cm
Now, surface area of small sphere = 4πr2 = 4π cm2