A ball of mass 0.9kg moving at 10m/s collide with another ball of equal mass at rest if after the impact the two balls move off together calculate common velocity (a) loss of energy

0.9 * 10 = (0.9 + 0.9) v

v = 5
initial ke = (1/2) * 0.9 * 100 = 45 Joules
final ke = (1/2) * 1.8 * 25 = 22.5 Joules