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I drive a distance of 200km around the city and my car’s average speed is 25 km/h.  How far do I then need to drive at an average speed of 100 km/h to raise my car’s average speed for the whole time to 40 km/h?

 Nov 28, 2019
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The original time  is   D / R  = 200/25  = 8 hrs

 

So.....he Total Distance is given by 200 + 100T     

Where T is the additional time driving at 100 km / hr

 

So    Total Distance / Total Time = 40

 

[200 + 100T ]

___________  =   40      cross-multiply

   8  +  T

 

200 + 100T  = 40 [ 8 + T]    simplify

 

200 + 100T  = 320 + 40T

 

60T  =  120      divide both sides by  60

 

T  =120 /60   =  2 additional hrs of driving at 100 km.hr  = (2) 100  = 200 additional km 

 

cool cool cool

 Nov 28, 2019
edited by CPhill  Nov 28, 2019

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