Let the original speed of the aircraft be x km/hr Therefore, duration of the flight=
600
x
hr Time taken by the aircraft at reduced speed = Time taken by the aircraft at original speed + 30 minutes ∴
600
x−200
−
600
x
=
30
60
⇒
120000
x(x−200)
=
1
20
⇒x2−200x−240000=0 ⇒x2−600x+400x−240000=0 ⇒(x−600)(x+400)=0 ⇒x=600orx=−400 But, the speed cannot be negative. So,x=600km/hr Therefore, the duration of the flight=