SOLUTION: I am very stuck can someone pleas help me?
Science and medicine. A plane flies 720 mi against a steady 30-mi/h headwind
and then returns to the same point with the wind. If the e
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-> SOLUTION: I am very stuck can someone pleas help me?
Science and medicine. A plane flies 720 mi against a steady 30-mi/h headwind
and then returns to the same point with the wind. If the e
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Question 76869: I am very stuck can someone pleas help me?
Science and medicine. A plane flies 720 mi against a steady 30-mi/h headwind
and then returns to the same point with the wind. If the entire trip takes 10 h, what is the plane’s speed in still air? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! A plane flies 720 mi against a steady 30-mi/h headwind and then returns to the
same point with the wind. If the entire trip takes 10 h, what is the plane’s speed in still air?
:
Not hard if you follow a logical procedure:
Let s = planes speed in still air:
Then:
(s-30) = speed against the wind
(s+30 = speed with the wind
:
Write a time equation: Time = dist/speed
:
Time out + time back = 10 hrs + = 10
:
Mult equation by (s-3)(s+30) to get rid of the denominators:
720(s+30) + 720(s-30) = 10(s-30)(s+30)
:
720s + 21600 + 720s - 21600 = 10(s^2 - 900)
:
1440s = 10s^2 - 9000
:
0 = 10s^2 - 1440s - 9000
:
Simplify, divide equation by 10; a simple quadratic equation:
s^2 - 144s - 900 = 0
:
This will factor to:
(s - 150)(s + 6) = 0
s = +150, this is the solution we want
:
Plane speed in still air is 150 mph>
:
Check:
against the wind: 720/120 = 6 hrs
With the wind is: 720/180 = 4 hrs
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Total round trip time is = 10 hrs
:
How about it, did this make sense to you?
