4.计算下面各题,能简算的要简算.
| $\frac{1}{2}+\frac{1}{5}-\frac{1}{4}$ | $\frac{4}{3}-\frac{1}{8}+\frac{7}{12}$ | $\frac{2}{9}+\frac{4}{5}+\frac{7}{9}+\frac{1}{5}$ |
| 2-$\frac{2}{7}$-$\frac{5}{7}$ | $\frac{5}{8}-(\frac{5}{8}-\frac{1}{2})$ | $\frac{2}{9}+(\frac{3}{4}-\frac{1}{2})$. |
19.把一张长方形的纸对折三次后的小长方形是原来长方形面积的( )
| A. | $\frac{1}{4}$ | B. | $\frac{1}{8}$ | C. | $\frac{1}{6}$ | D. | $\frac{1}{3}$ |
18.甲数和乙数互质,丙数是甲、乙两数的倍数,甲、乙、丙三数的最大公因数是( )
0 135916 135924 135930 135934 135940 135942 135946 135952 135954 135960 135966 135970 135972 135976 135982 135984 135990 135994 135996 136000 136002 136006 136008 136010 136011 136012 136014 136015 136016 136018 136020 136024 136026 136030 136032 136036 136042 136044 136050 136054 136056 136060 136066 136072 136074 136080 136084 136086 136092 136096 136102 136110 199269
| A. | 甲数 | B. | 乙数 | C. | 丙数 | D. | 1 |