Geometry Calculations
1. **Problem statement:** Calculate perimeter and area of various shapes, volumes, and paint coverage as described.
2. Circle with diameter 23 feet:
- Radius $r=\frac{23}{2}=11.5$ ft
- Area $=\pi r^2=\pi \times 11.5^2=\pi \times 132.25=415.48$ ft$^2$
- Circumference $=2\pi r=2\pi \times 11.5=72.26$ ft
3. Square with sides 1.4 cm:
- Perimeter $=4 \times 1.4=5.6$ cm
- Area $=1.4^2=1.96$ cm$^2$
4. Rectangular postage stamp 2.2 cm by 1 cm:
- Perimeter $=2(2.2+1)=6.4$ cm
- Area $=2.2 \times 1=2.2$ cm$^2$
5. Parallelogram with sides 4.5 ft and 12.2 ft, height = 3.6 ft:
- Perimeter $=2(4.5+12.2)=33.4$ ft
- Area $=\text{base} \times \text{height}=12.2 \times 3.6=43.92$ ft$^2$
6. Square state park with sides 6 miles:
- Perimeter $=4 \times 6=24$ miles
- Area $=6^2=36$ miles$^2$
7. Rectangular envelope 8 in by 14 in:
- Perimeter $=2(8+14)=44$ in
- Area $=8 \times 14=112$ in$^2$
8. Parallelogram sides 8 ft and 30 ft, height 4 ft:
- Perimeter $=2(8+30)=76$ ft
- Area $=30 \times 4=120$ ft$^2$
9. Swimming pool (rectangular prism): 50 m long, 30 m wide, 2.5 m deep:
- Volume $=50 \times 30 \times 2.5=3750$ m$^3$
10. Arena floor 40 m by 50 m, ceiling 8 m high:
- Volume $=40 \times 50 \times 8=16000$ m$^3$
- Volume in liters $=16000 \times 1000=16000000$ L
11. Air duct circular cross-section radius 18 in (1.5 ft), length 40 ft:
- Radius $r=\frac{18}{12}=1.5$ ft
- Volume of cylinder $=\pi r^2 h=\pi \times 1.5^2 \times 40=\pi \times 2.25 \times 40=282.74$ ft$^3$
- Surface area of side $=2\pi r h=2\pi \times 1.5 \times 40=376.99$ ft$^2$
- Paint needed equals lateral surface area $=376.99$ ft$^2$
12. Grain storage hemispherical shell radius 30 m:
- Volume hemisphere $=\frac{2}{3}\pi r^3=\frac{2}{3}\pi \times 30^3=\frac{2}{3}\pi \times 27000=56548.67$ m$^3$
- Surface area hemisphere (excluding base) $=2\pi r^2=2\pi \times 30^2=5654.87$ m$^2$
- Paint needed $=5654.87$ m$^2$
13. Tennis balls stacked in cylindrical can:
- Diameter of one ball = $d$, height of can = $3d$
- Circumference $=\pi d$ vs height $=3d$
- Since $3d > \pi d$ (approximately 3 > 3.14? No, actually $3 < 3.14$)
- Circumference $=3.14d$ is greater than height $=3d$
Final answers summarized.