19.口算:
0 159835 159843 159849 159853 159859 159861 159865 159871 159873 159879 159885 159889 159891 159895 159901 159903 159909 159913 159915 159919 159921 159925 159927 159929 159930 159931 159933 159934 159935 159937 159939 159943 159945 159949 159951 159955 159961 159963 159969 159973 159975 159979 159985 159991 159993 159999 160003 160005 160011 160015 160021 160029 199269
25÷5= | 36÷6= | 23+85= | 87-36= |
100-25= | 9×8= | 288+300= | 200-170= |
6×7= | 47+39= | 81÷9= | 550+550= |