6．口算：
0 139986 139994 140000 140004 140010 140012 140016 140022 140024 140030 140036 140040 140042 140046 140052 140054 140060 140064 140066 140070 140072 140076 140078 140080 140081 140082 140084 140085 140086 140088 140090 140094 140096 140100 140102 140106 140112 140114 140120 140124 140126 140130 140136 140142 140144 140150 140154 140156 140162 140166 140172 140180 199269
| 6-2.4= | 5.3+3.5= | 4.7+6= | 1-$\frac{4}{9}$= |
| 20×30= | 24×30= | 640÷8= | $\frac{1}{5}$+$\frac{4}{5}$= |
