Answers

  • qais
  • Content Quality
2016-03-25T15:47:31+05:30
Let the actual speed be v km/hour
actual speed of run,v = distance/time = 390/x km/hour
if this speed is increased by 4 km/hour, time will be 2 hours less
i.e
(390/v) - [390/(v+4)] = 2 hours
⇒390[(v+4-v)/v(v+4)]= 2
⇒780 = v²+4v
⇒v²+4v - 780 =0
⇒v²+30v -26v -780=0
⇒v(v+30) -26(v+30)=0
⇒(v+30)(v-26)=0
so, v= 26 km/hours , neglecting negative value
so, time, x = 390/26 = 15 hours 

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