Here's why:

* Conservation of Momentum: The total momentum of a closed system (like the three objects colliding) *always* remains constant. This means the momentum *before* the collision is *equal* to the momentum *after* the collision.

* Elastic vs. Inelastic Collisions:

* Elastic Collisions: Kinetic energy is conserved. Think of billiard balls colliding.

* Inelastic Collisions: Kinetic energy is *not* conserved. Some energy is lost to heat, sound, deformation, etc. Think of a car crash.

Important Points:

* Even in inelastic collisions, momentum is conserved. It's just that the energy distribution changes.

* The statement might be true in some specific scenarios, but it's not a universal truth. For example, if one object is stationary and the other two are moving towards it, the total momentum *could* be slightly higher *before* the collision, but only because the momentum of the stationary object is zero.