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. What is the duration of the flight ?

A. 3 hours

B. 2.4 hours

C. 1.4 hours

D. 1 hour

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Correct Answer : D.

Let the duration of the flight be x hours.
Then

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

\frac{600}{x} - \frac{1200}{2 x + 1} = 200

x (2 x + 1) = 3

2 x^{2} + x - 3 = 0

\Rightarrow (2 x + 3) (x - 1) = 0

Neglecting the negative value for x we get x = 1

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