Q75 of 227 Page 917

Match the following columns:























Column I



Column II



(a) The radii of the circular ends of a bucket in the form of frustum of a cone of height 30 cm are 20 cm and 10 cm respectively. The capacity of the bucket is ….. cm3. [Take π = 22/7]



(p) 2418π



(b) The radii of the circular ends of a conical bucket of height 15 cm are 28 and 20 cm respectively. The slant height of the bucket is …. cm.



(q) 22000



(c) The radii of the circular ends of a solid frustum of a cone are 33 cm and 27 cm and its slant height is 10 cm. The total surface area of the bucket is …. Cm2.



(r) 12



(d) Three solid metallic sphere of radii 3 cm, 4 cm and 5 cm are melted to form a single solid sphere. The diameter of the resulting sphere is … cm.



(s) 17


a—(q), b—(s), c—(p), d—(r)


a) Given: The radii of the circular ends of a bucket are 20 cm and 10 cm respectively.


Height of the bucket is 30cm


Bucket is in the shape of frustum.


Let V be the Volume of the Bucket(Frustum)


Volume of the frustum is given by: × h × (R2 + r2 + Rr) (here r and R are the radii of smaller and larger circular ends respectively)


V = × h × (R2 + r2 + R × r)


V = × 30 × (202 + 102 + 20 × 10)


V = × 30 × (400 + 100 + 200) = × 30 × (700)


V = × 30 × (700) = 22000 cm3


The capacity of the bucket is: 22000 cm3


b) Given: Height of the frustum of a cone: 15 cm


radii of the Circular ends: 28cm and 20 cm.



Here slant height h can be found by using Pythagoras theorem.


s2 = h2 + (R-r)2 (here R is 28cm and r is 20cm)


s2 = 152 + (28—20)2


s2 = 152 + (8)2


s2 = 225 + 64


s2 = 289


s = √289 = 17


Slant height 0f the Frustum is 17cm


c) Given: The radii of the end of a bucket are 33 cm and 27 cm and its slant height is 10 cm


TSA of a frustum of a cone = πl(r1 + r2) + πr12 + πr22 (here l , r1, r2 are the slant height, radii of the frustum)


Let S be the TSA of the Frustum.


S = πl(r1 + r2) + π(r2)2 + π(r1)2


S = π × 10 × (33 + 27) + π(33)2 + π(27)2


S = π(600 + 1089 + 729) = 2418π


TSA of frustum is 2418π.


d) Given: Three solid metallic sphere of radii 3 cm, 4 cm and 5 cm.


Volume of the Solid sphere is: πr3 (here r is the radius of the sphere).


Let V1 be the volume of the sphere with radius 3cm.


Let V2 be the volume of the sphere with radius 4cm.


Let V3 be the volume of the sphere with radius 5cm.


V1 = πr3 = π(3)3


V2 = πr3 = π(4)3


V3 = πr3 = π(5)3


Here,


Let V be the Volume of the sphere that is formed by melting the spheres with volumes V1 , V2 , V3 .


V = V1 + V2 + V3 = π(3)3 + π(3)3 + π(3)3


V = π(33 + 43 + 53) = π(27 + 64+ 125) = π(216)


V = π(216) = π(6)3


Here, we can see that radius of the Sphere is 6cm, diameter = 2 × 6 = 12cm


Diameter of sphere formed by melting spheres with volumes V1, V2 , V3 is 12cm


More from this chapter

All 227 →
73

A circus tent is cylindrical to a height of 4 m and conical above it. If its diameter is 105 m and its slant height is 40 m, the total area of canvas required is

74

Match the following columns:























Column I



Column II



(a) A solid metallic sphere of radius 8 cm is melted and the material is used to make solid right cones with height 4 cm and radius of the base 8 cm. How many cones are formed?



(p) 18



(b) A 20-m-deep well with diameter 14 m is dug up and the earth from digging is evenly spread out to form a platform 44 m by 14 m. the height of the platform is…..m.



(q) 8



(c) A sphere of radius 6 cm is melted and recast into the shape of a cylinder of radius 4 cm. then the height of the cylinder is ….. cm.



(r) 16:9



(d) The volumes of two sphere are in the ratio 64:27. The ratio of their surface areas is ….. .



(s) 5


76

Each question consists of two statements, namely, Assertion (A) and Reason (R). For selecting the correct answer, use the following code:

Assertion (A): If the radii of the circular ends of a bucket 24 cm high are 15 cm and 5 cm respectively, then the surface area of the bucket is 545 π cm2.


Reason (R): If the radii of the circular ends of the frustum of a cone are R and r respectively and its height is h, then its surface area is π {R2 + r2 + l(R - r)},where l2 = h2 + (R –r)2.

77

Each question consists of two statements, namely, Assertion (A) and Reason (R). For selecting the correct answer, use the following code:

Assertion (A): A hemisphere of radius 7 cm is to be painted outside on the surface. The total cost of painting at Rs 5 per cm2 is Rs 2300.


Reason (R): The total surface area of a hemisphere is 3πr2.