physics repost
posted by Jon .
A marksman at rest fires a 4.00kg gun that expels a bullet of mass 0.0140 kg with a velocity of 181 m/s. The marksman's mass is 81.0 kg. What is the marksman's velocity after firing the gun?
mc = 85kg
md = 0.0140
(0.0140)(181)/85
= .0298 m/s

Wouldn't it be
massbullet*velocitybullet=massmarksman*v
v then would be something different than your calcs. 
I guess its not suppose to be there. I got it somehow though. I don't know what to do now

solve for v.
v= massbullet/massmarksman * velocty bullet.
Algebra. 
my answer for this one was correct its not 0.0312

Yes, your answer was correct. You were right to add the mass of gun and marksman, since they move together. This assumes the ground he is standing on exerts no horizontal force, which is not strictly true after the shot is fired