To find the surface area that the farmer needs to refinish, we need to calculate the lateral surface area of the cylindrical silo. The formula for the lateral surface area \(A\) of a cylinder is given by:
\[ A = 2 \pi r h \]
where \(r\) is the radius and \(h\) is the height.
Given:
- Radius \(r = 4\) feet
- Height \(h = 30\) feet
- \(\pi \approx 3.14\)
Now, we can substitute the values into the formula:
\[ A = 2 \times 3.14 \times 4 \times 30 \]
Calculating this step by step:
- Calculate \(2 \times 3.14 = 6.28\).
- Calculate \(6.28 \times 4 = 25.12\).
- Calculate \(25.12 \times 30 = 753.6\).
Therefore, the lateral surface area of the silo is \(753.6\) square feet.
Finally, rounding to the nearest tenth, the farmer needs 753.6 square feet of aluminum to refinish the silo.