七 整理与复习
数的世界(1)
1: (1) 4∶5 4/5
(2) 5∶12 5/12
(3) 4∶5
2: 2/3×9/5=6/5 13/22÷26/33=3/4 7/10÷8/9×5/21=3/16
3:(1)3/5÷[﹙3/4-2/3﹚÷5/6]
= 3/5÷[1/12×6/5]
= 3/5×10
= 6
(2)13/14×49-9/14÷1/49
= 13/14×49-9/14×49
= 49×﹙13/14 -9/14)
= 49×2/7
= 14
4: (400-320)÷400
= 80÷400
= 20%
20%>15%
不能入库