The oil level rises by 7 cm per second. Convert to meters per hour:


\(7 \mathrm{~cm} / \mathrm{s}=0.07 \mathrm{~m} / \mathrm{s} \\
0.07 \times 3600=252 \mathrm{~m} / \text { hour }\)


The tank is a cylinder, so the volume filled per hour is the cross-sectional area times the height rise per hour:


\(\text { Volume rate }=\pi r^2 \times \text { (height rise per hour) }\)


Substitute the given values:


\(50688=\pi r^2 \times 252\)


Using \( \pi \approx \frac{22}{7} \) :


\(50688=\frac{22}{7} r^2 \times 252\)


Since \(252 \div 7=36\) :


\(50688=22 \times 36 \times r^2 \\
50688=792 \times r^2\)


Now divide:


\(r^2=\frac{50688}{792}=64 \\
r=8\)


Therefore, the radius is 8 meters.