SOLUTION: Please help me solve this word problem. I know the basic formula is rt=d but i don't know how to apply the words to the formula to solve. Joe flew 300 miles with the wind in two h

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Question 575446: Please help me solve this word problem. I know the basic formula is rt=d but i don't know how to apply the words to the formula to solve.
Joe flew 300 miles with the wind in two hours. After flying against the wind for two hours, he made 270 miles of the return trip. Find the wind speed and the speed of the plane in still air.

Found 3 solutions by solver91311, josmiceli, Edwin McCravy:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


If , then . Let represent the speed of the plane in still air and let represent the speed of the wind. When the plane is flying with the wind, the true speed of the plane is , and against the wind it is .

With the wind he goes 300 miles in 2 hours, so his true speed is 150. Against the wind he goes 270 miles in 2 hours, so his true speed is 135. So:





Solve the 2X2 system for and

John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism


Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +w+ = the wind speed
Let +p+ = the speed of the plane in still air
+p+%2B+w+ = speed of plane flying with the wind
+p+-+w+ = speed of plane flying against the wind
---------
given:
Equation flying with the wind:
(1) +300+=+%28+p+%2B+w+%29%2A2+
Equation flying against the wind:
(2) +270+=+%28+p+-+w+%29%2A2+
------------------
Add the equations:
(1) +2p+%2B+2w+=+300+
(2) +2p+-+2w+=+270+
+4p+=+570+
+p+=+142.5+
Plug this back into either equation
(1) +2p+%2B+2w+=+300+
(1) +p+%2B+w+=+150+
(1) +142.5+%2B+w+=+150+
(1) +w+=+7.5+
The speed of plane in still air is 142.5 mi/hr
The wind speed is 7.5 mi/hr
check answer:
(1) +300+=+%28+p+%2B+w+%29%2A2+
(1) +300+=+%28+142.5+%2B+7.5+%29%2A2+
(1) +300+=+150%2A2+
(1) +300+=+300+
and
(2) +270+=+%28+p+-+w+%29%2A2+
(2) +270+=+%28+142.5+-+7.5+%29%2A2+
(2) +270+=+135%2A2+
(2) +270+=+270+

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
You are asked for two speeds.  But actually there are four speeds to
consider:

1.  The speed at which the plane would be traveling if there was no wind,
    (which is not the case).   Let's call this speed x

2.  The speed of the wind.  Let's call this speed w.

3.  The faster speed with the wind.  This is the actual faster speed of the
    plane when the wind is blowing in the direction the plane is flying.  This
    speed is x+w.

4.  The slower speed against the wind.  This is the actual slower speed of the
    plane when the wind is blowing in the opposite direction to the direction
    the plane is flying.  This speed is x+w.


Joe flew 300 miles with the wind in two hours.
So we use the formula rt = d substituting (x+w) for r, 2 for t, and 300 for d:

                      rt = d
                  (x+w)2 = 300

We divide both sides by 2:

                     x+w = 150

After flying against the wind for two hours, he made 270 miles of the return trip.
So we use the formula rt = d again but this time substituting (x-w) for r, 
2 again for t, but only 270 for d:

                      rt = d
                  (x-w)2 = 270

We divide both sides by 2:

                     x-w = 135

So we have this system of equations to solve:

                     x+w = 150
                     x-w = 135

Solve that system and get x = 142.5 mph and w = 7.5 mph

The wind speed is 7.5 mph and the speed of the plane in still air is 142.5 mph.

Checking:

With the wind the plane was traveling 142.5+7.5 or 150mph, and in 2 hours
he traveled twice 150 or 300 miles.  That checks.
 
And against the wind the plane was traveling 142.5-7.5 or 135mph, and in 
2 hours he traveled twice 135 or 270 miles.  That checks. So we know the 
answers are correct.

Edwin