Working alone at it's own constant rate, a machine seals K cartons in 8 hours, and working alone at it's own constant rate, another machine seals K cartons in 4 hours. If the two machines, each working alone at it's own constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?
D) 66 and 2/3%
D. faster machine can do k in 4 hours
faster machine can do 2k in 8 hours
slower machine can do k in 8 hours
(faster + slower) machine can do (2k+k) in 8 hours
% of cartoons faster machine does = 2k/3k=2/3 of total or 67%