假如一隻船自身的速度是12miles/hr
而它要進行一個旅程
它要去上游(upsteam)距離是6miles，之然落番去
咁全程就用左64mins.
問題是:水流的速度是多少 miles/hr呢?
諘列式(步驟)
thz
數學問題，有關speed
2007-10-13 12:26 am
回答 (1)
2007-10-13 12:37 am
✔ 最佳答案
Let the speed of the stream be x mile/hr.Travlling up the stream, speed = (12 - x) mile/hr
Travelling down the stream, speed = (12 + x) mile/hr
Distance (each) = 6 miles.
Total time = 64 mins
So, 6 / (12 - x) + 6 / (12 + x) = 64 / 60
6/ (12 - x) + 6 / (12 + x) = 16 / 15
90 (12 + x) +90 (12 - x) = 16 (144 - x^2)
16x^2 +2160 - 2304 = 0
16x^2 = 144
x^2 = 9
x = 3
The speed of the stream is 3 miles/hr
收錄日期: 2021-04-13 13:53:32
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