prep 请教一题 多谢

ypl214

Working alone at its own constant rate, a machine seals k cartons in 8 hours,and working alone at its own constant rate, a second machine seals k cartons in 4 hours. If the two machines,each working at its own constant rate anf for the same period of time, together a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?
答案 66又三分之二

ypl214

是 66有三分之二%

liyingcai1988

慢的速度是k/8 per hour, 快的速度是k/4 per hour, 一起工作t hour后
慢的做了kt/8 cartons, 快的做了kt/4 cartons, 一共做了3kt/8 cartons
所以快的做了的百分比就是(kt/4)/(3kt/8)=2/3=66.6666667%