Two metallic right circular cones having their heights 9 cm and 18 cm...
To find the surface area of the sphere formed by melting and recasting the two cones, we need to follow these steps:
1. Find the volume of each cone:
- The volume of a cone can be calculated using the formula V = (1/3) * π * r^2 * h, where r is the radius and h is the height.
- For the first cone, with a height of 9 cm and a radius of 4√2 cm, the volume is V1 = (1/3) * π * (4√2)^2 * 9 = 96π cm^3.
- For the second cone, with a height of 18 cm and a radius of 4√2 cm, the volume is V2 = (1/3) * π * (4√2)^2 * 18 = 192π cm^3.
2. Find the total volume of the two cones:
- The total volume of the two cones is the sum of their individual volumes: V_total = V1 + V2 = 96π + 192π = 288π cm^3.
3. Find the radius of the sphere formed:
- The volume of a sphere can be calculated using the formula V = (4/3) * π * r^3, where r is the radius.
- Equating the volume of the sphere to the total volume of the two cones, we have: (4/3) * π * r^3 = 288π.
- Simplifying the equation, we get: r^3 = 216.
- Taking the cube root of both sides, we find: r = 6 cm.
4. Find the surface area of the sphere:
- The surface area of a sphere can be calculated using the formula A = 4 * π * r^2, where r is the radius.
- Plugging in the value of r, we have: A = 4 * π * 6^2 = 144π cm^2.
Therefore, the correct answer is option 'D', 144π.
Two metallic right circular cones having their heights 9 cm and 18 cm...
Volume of sphere = combined volume of the 2 cones
=
Let the radius of sphere be r
r = 6 cm
Hence, Surface Area of the sphere = 4π x 36 = 144 π
Hence, the correct option is (d).
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