Difficult# The Velocity of the Center of Mass

APPH12-JKS8W6

Two gliders, (X and Y), collided on a horizontal, frictionless air-track. Due to the velcro strips attached to each glider, they stuck together after the collision. The mass of glider X was 0.15 kg and its velocity before the collision was 0.27 m/s to the right (the positive direction). The mass of glider Y was 0.25 kg and its velocity before the collision was 0.19 m/s to the left.

What was the velocity of the center of mass of the two glider system before the collision?