The inclusive production of charmed particles in Z -> bb decays has been measured from the yield ofD0 , D+, D+s and Λ+c decays in a sample of qq events with high b purity collected with the ALEPH detector from 1992 to 1995. From these measurements, adding the charmonia production rate and an estimate of the charmed strange baryon contribution, the average number of charm quarks per b decay is determined to be nc = 1.230 +/- 0.036 +/- 0.038 +/- 0.053, where the uncertainties are due to statistics, systematic effects and branching ratios, respectively.
