1. **Problem 1: Three externally tangent circles with center distances 7, 8, and 9 inches. Find the area of the largest plate.**
2. The distances between centers of tangent circles equal the sum of their radii. Let the radii be $r_1$, $r_2$, and $r_3$ with $r_3$ largest.
3. We have:
$$r_1 + r_2 = 7$$
$$r_2 + r_3 = 8$$
$$r_3 + r_1 = 9$$
4. Add all three equations:
$$2(r_1 + r_2 + r_3) = 7 + 8 + 9 = 24$$
$$r_1 + r_2 + r_3 = 12$$
5. From $r_1 + r_2 = 7$, substitute into sum:
$$7 + r_3 = 12 \implies r_3 = 5$$
6. The largest radius is $r_3 = 5$ inches.
7. Area of largest plate:
$$\pi r_3^2 = \pi \times 5^2 = 25\pi$$
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8. **Problem 2: A chord of length 8 units is 3 units from the center of circle C. Find the area of circle C.**
9. Let radius be $r$. The perpendicular distance from center to chord is 3 units.
10. Using right triangle formed by radius, half chord, and distance to chord:
$$r^2 = 3^2 + \left(\frac{8}{2}\right)^2 = 9 + 16 = 25$$
11. Radius:
$$r = 5$$
12. Area of circle:
$$\pi r^2 = \pi \times 5^2 = 25\pi$$
**Final answers:**
- Largest plate area: $25\pi$
- Circle C area: $25\pi$
Circle Areas 218D06
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