3 hours

2.4 hours

1.4 hours

1 hour

D. 1 hour

Let the duration of the flight be x hours.

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

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

$x(2x+1)=3$

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

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

Neglecting the negative value for x we get x = 1