1,设进价为X:900*0.9-40-X=0.1*X
X=700
2,设它为X:X/6+(3900-X)/5=120
5x+3900*6-6x=120*30
x=3900*6-3600=19800>3900
说明第二题有问题:3900/6=650远远大于一共的两分钟
1,设进价为X:900*0.9-40-X=0.1*X
X=700
2,设它为X:X/6+(3900-X)/5=120
5x+3900*6-6x=120*30
x=3900*6-3600=19800>3900
说明第二题有问题:3900/6=650远远大于一共的两分钟