help~
2007-08-21 4:11 am
1.A coin with diameter 21mm and thickness 3mm is painted with black ink on its rim(邊緣).Then it is rolled on a paper so that a thin rectangle is drawn. If the area of the rectangle is 1980mm2(平方毫米),find how many turns has the coin rotated.(Take π equals 22/7)
回答 (1)
2007-08-21 4:19 am
✔ 最佳答案
周界=2πr,,2x22/7x21/2=66mmrectangle既闊=3mm...
rectangle既長=1980/3=660mm
the coin rotated= 660/66 = 10times...
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收錄日期: 2021-04-13 18:21:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070820000051KK04933