SOLUTION: Hi A plane took off 1 hour later for its destination 3000km away. In order to reach the destination on time the pilot increased speed by 500km per hour. What is the new sp

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Question 1153922: Hi
A plane took off 1 hour later for its destination 3000km away. In order to reach the destination on time the pilot increased speed by 500km per hour.
What is the new speed of the plane.
Thanks

Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
.

Let x be the new speed, in km/h.

Then the regular speed is (x-500) km/h.


The regular flight time is   hours.

The new time flight is       hours.


The difference is one hour (1 hour), which gives you THIS "time equation"


     -  = 1   hour.


To solve the equation, multiply both sides by  x*(x-500).  You will get


    3000x - 3000*(x-500) = x*(x-500)

    300*500 = x*(x-500)

    x^2 - 500x - 1500000 = 0

     =  =  = .


Only positive root makes sense  x =  = 1500.


ANSWER.  The new speed is 1500 km/h.


CHECK.   The regular speed is then 500 km/h lover, i.e.  1000 km/h.


         Check the "time equation"   -  = 3 - 2 = 1 hour.   ! Precisely correct !

Solved.


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