Center Of Mass

Two masses '\(m_{\mathrm{a}}\)' and '\(\mathrm{m}_{\mathrm{b}}\)' moving with velocities '\(v_{\mathrm{a}}\)' and '\(v_{\mathrm{b}}\)' opposite directions collide elastically. Alter the collision '\(m_a\)' and '\(m_b\)' move with velocities and '\(v_{\mathrm{b}}\)' and '\(v_a\)' respectively, then the ratio \(\mathrm{m_a:m_b}\) is