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Answer

Let D be the distance travelled.

  SPEED    |      TIME = DISTANCE / SPEED
=============================================================      
  60km/h:  |----------- D / 60 -------------------| 9:15
  72km/h:  |----------- D / 72 --------| 8:50

So we can see from the diagram that the difference in time taken
is 25 minutes = 25/60 hour.

So 25/60 = D/60 - D/72 = D (1/60 - 1/72)
      25 = D (1 - 60/72) = D (1 - 5/6) = D (1/6)

So Distance = 6 x 25 = 150km.
CHECK:
  Time taken at 60km/h = 150 / 60 = 2.5 = 2 h 30 min
  Time taken at 72km/h = 150 / 72 = 25 / 12 = 125 / 60 = 2 h 5 min
So savings of 25 minutes.

 

1 Reply 1 Like

Paiseh ➡  so sorry for my earlier wrong answer…

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