  Branching fractions of the decays $H_b\to H_c\pi^-\pi^+\pi^-$ relative to
$H_b\to H_c\pi^-$ are presented, where $H_b$ ($H_c$) represents B^0-bar($D^+$),
$B^-$ ($D^0$), B_s^0-bar ($D_s^+$) and $\Lambda_b^0$ ($\Lambda_c^+$). The
measurements are performed with the LHCb detector using 35${\rm pb^{-1}}$ of
data collected at $\sqrt{s}=7$ TeV. The ratios of branching fractions are
measured to be
  B(B^0-bar -> D^+\pi^-\pi^+\pi^-)/ B(B^0-bar -> D^+\pi^-) = 2.38\pm0.11\pm0.21
  B(B^- -> D^0\pi^-\pi^+\pi^-) / B(B^- -> D^0\pi^-) = 1.27\pm0.06\pm0.11
  B(B_s^0-bar -> D_s^+\pi^-\pi^+\pi^-) / B(B_s^0-bar -> D_s^+\pi^-) =
2.01\pm0.37\pm0.20
  B(\Lambda_b^0->\Lambda_c^+\pi^-\pi^+\pi^-) / B(\Lambda_b^0 ->
\Lambda_c^+\pi^-) = 1.43\pm0.16\pm0.13.
  We also report measurements of partial decay rates of these decays to excited
charm hadrons. These results are of comparable or higher precision than
existing measurements.
