The cross section of a steel pipe is annular. The inner diameter is 6cm and the ring width is 2cm. How many square centimeters is the cross section area of the steel pipe?

The cross section of a steel pipe is annular. The inner diameter is 6cm and the ring width is 2cm. How many square centimeters is the cross section area of the steel pipe?

Cross sectional area = 3.14 × (6-2) &# 178; - 3.14 × ((6-2) × 2) &# 178; = 3.14 × 9-3.14 × 4 = 15.7 square centimeter
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The cross section of a steel pipe is annular, the inner diameter is 8 decimeters, the outer diameter is 10 decimeters, how many square decimeters is the cross section area of the steel pipe?

3.14 × [(10 △ 2) 2 - (8 △ 2) 2] = 3.14 × [25-16], = 3.14 × 9, = 28.26 (square decimeter); answer: the cross-sectional area of steel pipe is 28.26 square decimeter