1. **State the problem:** We need to find the surface area of a gas tank shaped as a cylinder with two hemispheres attached at each end. 2. **Given:** - Total length of tank = 77 cm - Length of cylindrical part = 35 cm - Radius of each hemisphere = $r = \frac{77 - 35}{2} = 21$ cm 3. **Formulas:** - Surface area of a sphere = $4 \pi r^2$ - Surface area of a hemisphere = half of sphere surface area = $2 \pi r^2$ - Surface area of a cylinder (excluding bases) = $2 \pi r h$ 4. **Calculate surface area of hemispheres:** Since there are two hemispheres, their combined surface area equals the surface area of one full sphere: $$\text{Area}_{hemispheres} = 2 \times 2 \pi r^2 = 4 \pi r^2$$ 5. **Calculate surface area of the cylindrical part:** $$\text{Area}_{cylinder} = 2 \pi r h = 2 \pi \times 21 \times 35 = 1470 \pi$$ 6. **Total surface area:** $$\text{Area}_{total} = \text{Area}_{hemispheres} + \text{Area}_{cylinder} = 4 \pi r^2 + 2 \pi r h$$ Substitute $r=21$ and $h=35$: $$= 4 \pi (21)^2 + 2 \pi (21)(35) = 4 \pi (441) + 1470 \pi = 1764 \pi + 1470 \pi = 3234 \pi$$ 7. **Calculate numerical value:** $$3234 \pi \approx 3234 \times 3.1416 = 10163.4$$ 8. **Final answer:** The surface area of the gas tank is approximately **10163.4 cm²** to 1 decimal place.