Abstract
We calculate the semileptonic branching fraction and charm yield from inclusive B decays using the formalism of perturbative QCD. For nonleptonic decays, we employ the modified factorization theorem, in which Wilson coefficients evolve with the characteristic scales of the decay modes. It is found that the decay rate of the single-charm mode b→cūd is enhanced, and a lower B SL is obtained without increasing n c . This conclusion differs from the usual one, where the b-→cc̄s mode is increased. Our result for the B meson lifetime is also consistent with the data.