according to conservation of momentum , in absence of external forces , the total momentum of system of the particles remain same both before and after collision.
momentum of colliding objects before collision = momentum of colliding objects after collision.
or
m1 v1i + m2 v2i = m2 v1f + m2 v2f
where m1 and m2 are the two colliding objects. v1i and v2i are their respective initial velocities before collision and v1f and v2f are their respective final velocities after collision.
hence the correct statement is
total momentum before the collision is equal to the momentum after collision.
