Spherical Shell Wire
1. **Problem statement:**
A metallic spherical shell has an external radius of 6 cm and thickness of 1 cm. It is melted and drawn into a wire of diameter 2 cm. If 1 cm of the wire is sold at 3, find the total price of the wire.
2. **Step 1: Calculate the volume of the spherical shell.**
The volume of a spherical shell is given by the difference of volumes of two spheres:
$$V = \frac{4}{3}\pi (R^3 - r^3)$$
where $R$ is the external radius and $r$ is the internal radius.
Given:
$R = 6$ cm
Thickness $= 1$ cm, so internal radius $r = R - 1 = 5$ cm
Calculate volume:
$$V = \frac{4}{3}\pi (6^3 - 5^3) = \frac{4}{3}\pi (216 - 125) = \frac{4}{3}\pi (91) = \frac{364}{3}\pi \text{ cm}^3$$
3. **Step 2: Calculate the volume of the wire.**
The wire is cylindrical with diameter 2 cm, so radius $r_w = 1$ cm.
Let the length of the wire be $L$ cm.
Volume of wire:
$$V = \pi r_w^2 L = \pi (1)^2 L = \pi L \text{ cm}^3$$
4. **Step 3: Equate volumes to find length $L$.**
Since the shell is melted and reshaped into the wire, volumes are equal:
$$\pi L = \frac{364}{3}\pi$$
Divide both sides by $\pi$:
$$L = \frac{364}{3} = 121.33 \text{ cm}$$
5. **Step 4: Calculate the price of the wire.**
Price per cm of wire = 3
Length of wire = 121.33 cm
Total price:
$$\text{Price} = 3 \times 121.33 = 364$$
**Final answer:** The wire will fetch 364.