ProblemA=πr2, r=7A = \pi r^2,\ r = 7A=πr2, r=7Step-by-step solution套用公式：A=πr2A = \pi r^2A=πr2。代入 r=7r = 7r=7：A=π⋅72=49πA = \pi \cdot 7^2 = 49\piA=π⋅72=49π。取近似值：49π≈153.9449 \pi \approx 153.9449π≈153.94。AnswerA=49π≈153.94A = 49\pi \approx 153.94A=49π≈153.94Want to solve a different problem? Open the area solver →Related worked examples/solve/geometry/area-rectangle-5-by-8