The collision of black holes and the emission of gravitational radiation in higher-dimensional spacetimes are of interest in various research areas, including the gauge-gravity duality, the TeV gravity scenarios evoked for the explanation of the hierarchy problem, and the large-dimensionality limit of general relativity. We present numerical simulations of head-on collisions of nonspinning, unequal-mass black holes starting from rest in general relativity with $4\le D\le 10$ spacetime dimensions. We compare the energy and linear momentum radiated in gravitational waves with perturbative predictions in the extreme mass ratio limit, demonstrating the strength and limitations of black-hole perturbation theory in this context.