Three solid spheres of radius 3 cm 4 cm and 5 cm are melted and recasted into a solid sphere What wi...........

Quantitative Aptitude (CGL) Mensuration 3D

Three solid spheres of radius 3 cm, 4 cm and 5 cm are melted and recasted into a solid sphere. What will be the percentage decrease in the surface area?

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Explanation:

Total Surface area before melting=4*3.14(3*3+4*4+5*5)=4*3.14*50=200*3.14
Total VOlume Before=Total Volume After
4/3 * 3.14 (3*3*3+4*4*4+5*5*5)=4/3 * 3.14 * r^3
27+64+125=r^3
r=6
Total Surface area after melting = 4*3.14*6*6=144*3.14
Total Decrease in surface area=200*3.14 - 144*3.14 = 56*3.14
Decrease %=56*3.14*100 / 200*3.14= 28