regarding another momentum problem

[Zuloft]

a 4kg object travelling west a 25 m/s hots a 15 kg object at rest. the 4 kg object bounces eastward at 8 m/s. what is the speed and direction of the 15 kg object.

i set it up at

(m1)(v1)+(m2)(v2)= (mtotal)(vfinal)
100/ 19 = x
5.26 = x

except i solvedfor the final v
IM STUMPED anything on what i did wrong?:yuck:

[G01]

your problem here is your formula. You are using a formula where the two objects stick together after the collision. (Inelastic) instead of one where they bounce off.(elastic)