5．口算与估算题
| 750-430= | 960-500= | 94880-75023≈ | 95740+74999≈ |
| 420+80= | 730+90= | 270+60= | 95080+24910≈ |
| 15万+25万= | 73万-26万= | 25亿+63亿≈ | 90万-68万= |
2．求末知数x
0 161840 161848 161854 161858 161864 161866 161870 161876 161878 161884 161890 161894 161896 161900 161906 161908 161914 161918 161920 161924 161926 161930 161932 161934 161935 161936 161938 161939 161940 161942 161944 161948 161950 161954 161956 161960 161966 161968 161974 161978 161980 161984 161990 161996 161998 162004 162008 162010 162016 162020 162026 162034 199269
| 3108-x=100 | x-8807=2799 | x+4216=5743 |