Quasielastic scattering and deuteron breakup in the 200 MeV region is studied by impinging a pulsed neutron beam on a deuterium target at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center. The scattered neutrons from the d(n,np)n reaction are detected by a wall of neutron time-of-flight scintillators, and scattered protons are detected by two scintillators and a wire chamber. This setup allows for measurement of the incident neutron energy, scattered neutron energy, and scattered proton energy, as well as the scattering angle and position of the scattered neutron. The results of the experiment are compared with a Monte Carlo simulation of neutron-proton scattering, to observe the differences between two-body and three-body quasielastic collisions. The four-dimensional differential cross section for the d(n,np)n reaction is determined from the data.