Perfectly Inelastic Collision

1 question from 1 paper, each with its answer.

Concepts tested

1 Work, Energy and Power Easy

Two bodies A and B of same mass undergo completely inelastic one dimensional collision. The body A moves with velocity $v_1$ while body B is at rest before collision. The velocity of the system after collision is $v_2$. The ratio $v_1 : v_2$ is;