A bullet comes out of a gun with a velocity of 600 m/s. At what height from the target should the gun be aimed in order to hit the target situated at a distance of 200 m from the gun?

Time taken in travelling horizontal distance of 200m with constant velocity of 600 m/s is equal to 200/600=1/3 sec. 

Vertical distance moved under acceleration due to gravity, with zero initial velocity will be

 $\mathrm{S}=\mathrm{ut}+\frac{1}{2}{\text{ at }}^2=0+\frac{1}{2}\times 10\times (1/3{)}^2=0.55 \mathrm{m}\text{ . }$

Hence the bullet should be aimed 0.55 m higher than target.