. The internal and external diameters of hollows hemispherical vessel are 24 cm and 25 cm respectively. If the cost of painting 1 cm2 of the surface are
A. Rs. 90.05
B. Rs. 92.25
C. Rs. 95.20
D. Rs. 96.29
Best Answer
Answer ||| D
Solution |||
Internal radius = 12 cm and external radius = 12.5 cm.
Total area to be painted = external area + internal area + area of ring
= 2
R2 + 2r2 + (R2 – r2)
= (2R2 + R2 + 2r2 – r2)
= (3R2 + r2)
= 
[ (3 x 12.5 x 12.5) + (12 x 12) ]
= 1925.78 cm2
Total cost = 1925.78 x 0.05 = 96.29 Rs.
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