Thd internal and external radius of a hollow hemispherical vessel are 12cm and 25/2 cm respectively. The cost of painting 1sqcm of surface is 0.07.find the total cost to paint the vessel
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The internal and external diameters of a hollow hemispherical vessel are 24cm and 25cm, respectively. The cost to paint 1 cm
2
surface is Rs.0.05. Find the total cost to paint the vessel all over. (use π=
7
22
)
Medium
Solution
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Correct option is D)
Internal diameter=24cm, Internal radius,r
1
=12cm
External diameter=25cm, External radius,r
2
=12.5cm
surface area of hemispherical vessel to be pointed =CSA of external hemisphere+CSA of internal hemisphere+area of top
=2πr
2
2
+2πr
1
2
+π(r
2
2
−r
1
2
)
=π(3r
2
2
+r
1
2
)=
7
22
(3×1.5
2
+12
2
)
=
7
22
(3×156.25+144)=
7
22
×612.75
=
7
13480.5
cm
2
total cost of painting=
7
13480.5
×0.05=Rs96.28
≈Rs96