1. **Problem 9:** Find the perimeter and area of a semicircle with diameter 5.2 ft. 2. **Formula:** - Radius $r = \frac{d}{2}$ - Perimeter of semicircle $P = \pi r + d$ - Area of semicircle $A = \frac{1}{2} \pi r^2$ 3. **Calculate radius:** $$r = \frac{5.2}{2} = 2.6 \text{ ft}$$ 4. **Calculate perimeter:** $$P = 3.14 \times 2.6 + 5.2 = 8.164 + 5.2 = 13.364 \text{ ft}$$ 5. **Calculate area:** $$A = \frac{1}{2} \times 3.14 \times (2.6)^2 = 0.5 \times 3.14 \times 6.76 = 10.6132 \text{ ft}^2$$ --- 1. **Problem 10:** Find the perimeter and area of a semicircle with diameter 36 mm. 2. **Calculate radius:** $$r = \frac{36}{2} = 18 \text{ mm}$$ 3. **Calculate perimeter:** $$P = 3.14 \times 18 + 36 = 56.52 + 36 = 92.52 \text{ mm}$$ 4. **Calculate area:** $$A = \frac{1}{2} \times 3.14 \times (18)^2 = 0.5 \times 3.14 \times 324 = 508.68 \text{ mm}^2$$ --- 1. **Problem 11:** Macy's circular pool diameter is 18 ft. Find distance swimming 4 times around. 2. **Calculate radius:** $$r = \frac{18}{2} = 9 \text{ ft}$$ 3. **Calculate circumference:** $$C = 2 \pi r = 2 \times 3.14 \times 9 = 56.52 \text{ ft}$$ 4. **Distance for 4 laps:** $$4 \times 56.52 = 226.08 \text{ ft}$$ --- 1. **Problem 12:** Lighthouse light radius 20 miles, find total area lit. 2. **Calculate area of circle:** $$A = \pi r^2 = 3.14 \times 20^2 = 3.14 \times 400 = 1256 \text{ miles}^2$$