Two balls with masses m1 = 100 g and m2 = 200 g are moving towards each other. With what speed will these balls

Two balls with masses m1 = 100 g and m2 = 200 g are moving towards each other. With what speed will these balls move and in what direction if after impact they move as a whole? The velocities of the balls are respectively equal to V1 = 4 m / s and V2 = 3 m / s.

Condition:
m1 = 100 g = 0.1 kg.
m2 = 200 g. = 0.2 kg.
V1 = 4 m / s.
V2 = 3 m / s.
To find :
V3 -? m / s.
Decision :
m2 * V2-m1 * V1 = (m1 + m2) * V3.
V3 = (m2 * V2-m1 * V1) / (m1 + m2).
[] = (kg * m / s * m / s – kg * m / s * m / s) / kg + kg = kg * m / s / kg = m / s.
V3 = (0.2 * 3-0.1 * 4) / (0.1 + 0.2) = 0.2 / 0.3 = 2/3 = 0.66667 = 0.7 (m / s).
Answer: about 0.7 m / s.