13．把棱长为6厘米的两个正方体拼成一个长方体，表面积减少（ ）平方厘米．
| A． | 72 | B． | 36 | C． | 108 | D． | 18 |
10．直接写得数
0 132024 132032 132038 132042 132048 132050 132054 132060 132062 132068 132074 132078 132080 132084 132090 132092 132098 132102 132104 132108 132110 132114 132116 132118 132119 132120 132122 132123 132124 132126 132128 132132 132134 132138 132140 132144 132150 132152 132158 132162 132164 132168 132174 132180 132182 132188 132192 132194 132200 132204 132210 132218 199269
| $\frac{1}{3}$-$\frac{1}{4}$= | $\frac{2}{5}$+$\frac{3}{10}$= | 6×$\frac{2}{3}$= | 2-$\frac{4}{5}$= |
| $\frac{5}{8}$×$\frac{2}{5}$= | $\frac{1}{20}$×$\frac{5}{7}$= | $\frac{8}{7}$×$\frac{7}{16}$= | $\frac{1}{9}$+$\frac{5}{6}$+$\frac{8}{9}$= |