In a flight of 600km, an aircraft was slowed down due to bad whether. Its average speed for the trip   was reduced by 200 km/hr and the time of flight increased by 30 min. The duration of the flight is:

Let the original speed of  aircraft is ‘x’ kmphs

Due to bad weather, speed reduced = (x – 200) kmph

Duration of  the flight at original speed $\Rightarrow \frac{600}{x}$

Duration of  the flight speed reduced $\Rightarrow \frac{600}{x-200}hrs$

$\therefore$ Time of  flight increased = 30 mins

$\left(\frac{600}{x-200}\right)-\frac{600}{x}=\frac{30}{60}=\frac{1}{2}$

$\frac{600x-600x+120000}{x^2-200x}=\frac{1}{2}$

$x^2-200x-120000=0$

$(x-600)(x+400)=0$

$x=600\Rightarrow durationoftheflight\Rightarrow \frac{600}{600}=1hr$

Speed can’t be Negative.