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A motorist travelling at a steady speed of 120km/h covers a section of the highway in 30min. After a speed limit is imposed he finds that when travelling at the maximum speed allowed he takes 20 min. longer than before to cover the same section.

Calculate the speed limit.

  • math -

    If he travels at 120 Km per hour in 30'(ie 1/2 hour) he did 120/2=60Km.
    If he travels at max speed allowed he takes 30+20=50'or 50/60=5/6 hours to reach his destination. so speed is: 60/(5/6)= 360/5=72Km/h

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