Tailwind headwind

azorn12

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Jan 10, 2012
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How would you set up this problem?

Flying to Kampala with a tailwind a plane averaged 158 km/h. On the return trip the plane only averaged 112 km/h while flying back into the same wind. Find the speed of the wind and the speed of the planed in still air.
 
How would you set up this problem?

Flying to Kampala with a tailwind a plane averaged 158 km/h. On the return trip the plane only averaged 112 km/h while flying back into the same wind. Find the speed of the wind and the speed of the planed in still air.

What have you done on this so far?

You are looking for the wind speed and the speed of the plane in still air. Have you assigned variables to each of these things?

Let w = wind speed
Let a = speed of plane in still air

Then, have you translated the conditions of the problem into equations?

For example, the problem says that "flying WITH a tailwind, a plane averaged 158 km/hr". A tailwind PUSHES the plane and makes it go faster. The speed of the plane in still air is INCREASED by the wind speed. So, flying with the wind, the actual speed of the plane is

a + w

and we know that is 158 km/hr, so

a + w = 158

Now, there's another condition in the problem that needs to be translated into an equation as well. Once you have TWO equations, you can solve the system to find the values of "a" and "w" which make both equations true.

See what you can do to finish the problem!
 
Continuing on with Mrspi's explanation we have:

a + w = 158;
we also know that
a- w = 112

We now need to add the 2 equations

a + w = 158
+ a - w = 112
2a = 270
a = 135

Now we plug that back into one of the formulas.
135 - w = 158; which gives us
w = 23

Now we can substitute the value of a and w and see if the answers we got are true.

135 + 23 = 158 true 8-)
135 - 23 = 112 true also:-D
 
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