In a flight of 600 km, an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by 200 km/hr and the time of flight increased by 30 minutes. The duration of the flight is:
option
(a) 1 hour
(b) 2 hours
(c) 3 hours
(d) 4 hours

• suppose avg speed of aircraft is v km/hr,and it takes t hr to trip 600 km.
  then t=600/v.......(1)
  now avg speed slowed down by 200 km/hr and it takes 30 more minutes that means now it takes t+30/60=t+1/2 hr and speed is v-200
  now time=distance/speed=>t+1/2=600/(v-200)
  2t+1=1200/(v-200)
  (2t+1)(v-200)=1200
  (2t+1)((600/t)-200))=1200 from (1)
  on solving it t= -3/2 or 1
  time cant be -ve,hence answer is 1 hr.
• 13 years agoHelpfull: Yes(3) No(0)
• d=600km
  v*t=600
  v*t=(t+1/2)*(v-200)
  200=v-400t........................(a)
  v=600/t..........................(b)
  put the value of v in eq a
  2t^2+t-3=0
  t=1,-1.5
  t=1hr................ans
• 9 years agoHelpfull: Yes(0) No(0)