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hung	2006-11-10 12:16
Help on Maths A plane flies at a speed of 800 miles per hour in still air. It takes 15 minutes longer to fly 1260 mils into the wind than it takes to fly 1320 with the wind. Find the speed of the wind please help

kylau

2006-11-10 18:13

Q: A plane flies at a speed of 800 miles per hour in still air. It takes 15 minutes longer to fly 1260 mils into the wind than it takes to fly 1320 with the wind. Find the speed of the wind

A: Let the speed of the wind be v miles/h
t be the time in hour that the plane needs to fly 1320 with the wind

By Speed = Distance / Time

(800+v) = 1320/ t ..........(1)

(800-v) = 1260/ (t+1/4).........(2)

(1)+(2), then simplification gives a quadratic equation in t
160t^2-218t-33 = 0

t=1.5, -0.1375(rejected)

So sub into (1) gives v =80

Obadiah	2006-11-10 18:13
有冇中文版... 唔識做英文數...

Obadiah	2006-11-10 18:15
*引用第1樓kylau於2006-11-10 18:13發表的“”*: Q: A plane flies at a speed of 800 miles per hour in still air. It takes 15 minutes longer to fly 1260 mils into the wind than it takes to fly 1320 with the wind. Find the speed of the wind A: Let the speed of the wind be v miles/h t be the time in hour that the plane needs to fly 1320 with the wind ....... 好勁

kylau	2006-11-10 18:23
*引用第2樓江戶川柯南於2006-11-10 18:13發表的“”*: 有冇中文版... 唔識做英文數... although you may be a student from Chinese-medium school, you should try to understand the meaning. It is a very good training to your English, especially many mathematical articles and websites are in English. Get a yahoo dictionary when you need help on certain words

wil	2006-11-10 18:55
*引用第4樓kylau於2006-11-10 18:23發表的“”*: although you may be a student from Chinese-medium school, you should try to understand the meaning. It is a very good training to your English, especially many mathematical articles and websites are in English. Get a yahoo dictionary when you need help on certain words agree

hung	2006-11-10 23:36
*引用第1樓kylau於2006-11-10 18:13發表的“”*: Q: A plane flies at a speed of 800 miles per hour in still air. It takes 15 minutes longer to fly 1260 mils into the wind than it takes to fly 1320 with the wind. Find the speed of the wind A: Let the speed of the wind be v miles/h t be the time in hour that the plane needs to fly 1320 with the wind ....... thank you so much

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