(c) v2​=v1​1​+v2​1​. Velocity is uniform in both cases; that is, acceleration is zero.x=v1​t1​⇒t1​=v1​x​x=v2​t2​ ⇒t2​=v2​x​ Total displacement, x=v2​t2​⇒t2​=v2​x​ Total time, x′=2x∴  Average velocity, t=t1​+t2​⇒v2​=v1​1​+v2​1​