SOLUTION: I need some assistance please. Two cities are 1000 miles apart. On the first flight a plane flew into a 50 mph headwind. On the return flight the plane had 50 mph tailwind. The

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Question 873649: I need some assistance please.
Two cities are 1000 miles apart. On the first flight a plane flew into a 50 mph headwind. On the return flight the plane had 50 mph tailwind. The round trip flight was 4.5 hours. What is the average speed of the plane without the wind?
A. 480 mph
B. 450 mph
C. 375 mph
D. 325 mph
Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!


Hi

 t = D/r



     

 9r^2-2000r -22500 = 0,  r = 450 mph




 
Solved by pluggable solver: SOLVE quadratic equation with variable


Quadratic equation  (in our case ) has the following solutons:

  

  

  

  For these solutions to exist, the discriminant  should not be a negative number.

  

  First, we need to compute the discriminant : .

  

  Discriminant d=16810000 is greater than zero. That means that there are two solutions: .

  

    

    

    

    Quadratic expression  can be factored:

  

  Again, the answer is: 450, -5.55555555555556.
Here's your graph:





  

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