Question : The radius of a metallic spherical ball is 3 cm. If the metallic ball is melted and recast into $x$ number of hemispheres of radius equal to half the radius of the metallic spherical ball, then find the value of $x$.
Option 1: 15
Option 2: 14
Option 3: 16
Option 4: 13
Correct Answer: 16
Solution : Given, Radius of sphere = 3 cm = $r_s$ Radius of hemisphere = $\frac{r_s}{2}$ = $r_h$ ⇒ $r_s=2r_h$ We know, Volume of sphere = $x$(Volume of hemisphere) [in this case] ⇒ $\frac43\pi r_s^3=x(\frac23\pi r_h^3)$ ⇒ $2(2r_h)^3=x(r_h)^3$ ⇒ $x=2\times2\times2\times2$ ⇒ $x=16$ Hence, the correct answer is 16.
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Question : A solid sphere made of wax of radius 12 cm is melted and cast into solid hemispheres of radius 4 cm each. Find the number of such solid hemispheres.
Option 1: 54
Option 2: 27
Option 3: 14
Option 4: 28
Question : Three spherical balls of radius 2 cm, 4 cm, and 6 cm are melted to form a new spherical ball. In this process, there is a loss of 25% of the material. What is the radius (in cm) of the new ball?
Option 1: 6
Option 2: 8
Option 3: 12
Option 4: 16
Question : A solid metallic sphere of radius x cm is melted and then drawn into 126 cones each of radius 3.5 cm and height 3 cm. There is no wastage of material in this process. What is the value of $x$?
Option 1: 10.5
Option 2: 3.5
Option 3: 7
Option 4: 21
Question : A solid metallic sphere of radius 8.4 cm is melted and recast into a right circular cylinder of radius 12 cm. What is the height of the cylinder? (Your answer should be correct to one decimal place.)
Option 1: 6.5 cm
Option 2: 5.5 cm
Option 3: 7.0 cm
Option 4: 6.0 cm
Question : A 9 cm solid metallic cube and a solid metallic cuboid having dimensions 5 cm, 13 cm, and 31 cm are melted and recast into a single cube, What is the total surface area (in cm2) of the new cube?
Option 1: 865
Option 2: 1176
Option 3: 1362
Option 4: 2744
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