iMath 圖形的周界 (II) iMath Perimeter (II) app for iPhone and iPad

鐘面上的分針長 7 厘米, 過了 15 分鐘後, 分針的針尖移動了多少?
鐘面上的時針長 5 厘米, 過了 4 小時後, 時針的針尖移動了多少?

要找出以上兩條問題的答案, 你必須認識圓周率,並懂得計算圓周。
圓周 = 直徑 x 圓周率π
圓周 = 半徑 x 2 x 圓周率π

通過此活動, 掌握計算圓周的技巧, 並嘗試利用圓周, 進一步挑戰自己, 計算一些涉及圓周的多邊形的周界。


The minute hand on the clock is 7 cm long. After 15 minutes, how far would the tip of the minute hand have moved?
The hour hand on the clock is 5 cm long. After 4 hours, how far would the tip of the hour hand have moved?

To find the answers to the above two questions, you must know π, and know how to calculate circumference.
Circumference = Diameter x π
Circumference = Radius x 2 x π

Through this activity, you will learn to use π, and through it, challenge yourself and learn to find the perimeter of more different shapes.