On this year's teacher's day, Xiao Hong made a semicircular greeting card for her teacher with colored cardboard. For the sake of beauty, she bought a rope to stick it on the outside of the card It took 41.12 meters of rope to make this card. How many square centimeters of cardboard did he use?

41.12 = card diameter (d) + 1 / 2 card perimeter = D + 1 / 2 times 3.14d = D + 1.57d = 2, 57d
Let the diameter be X,
2.57x=41、12
x =16
Straight board times 2 = (16 divided by 2) times (16 divided by 2) times 3, 14 = 8 times 8 times 3, 14 = 64 times 3, 14 = 200, 96
Straight plate = 200, 96 divided by 2 = 100, 48 (square centimeter)

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