Help with application of calculas (1 Viewer)

[carlytse621]

<DIR>A stone is let fall from a tall building and 1 second later another stone is projected vertically downward with a velocity 20m/s. When will the second stone overtake the first?

thanks~
</DIR>

 

[Drongoski]

Is the answer: (40 - g)/2(20 - g) secs ??