PHYSICS
posted by kelsey .
On a horizontal frictionless table, masses A and B (3 kg, 6 kg) slide to the right and left, respectively. They have speeds of 3 m/s and 1 m/s, respectively. The two masses collide, and bounce off each other. After the collision, they travel in opposite directions at speeds of 1.5 m/s and 1.250 m/s, respectively.
Calculate the kinetic energy of the A+B system:
before collision:
after collision

They tell you the masses of both and their speeds before and after the collision. All you have to do is calculate and add up the kinetic energies (1/2) M V^2 of each mass, before and after.
They have already provided velocities that satisfy the momentum conservation requirement, so you don't have to apply conservation laws to do this problem.