3．直接写出得数：
| $\frac{2}{3}$×$\frac{6}{7}$= | $\frac{2}{5}$÷$\frac{3}{10}$= | $\frac{4}{5}$+$\frac{1}{10}$= | $\frac{3}{7}$-$\frac{1}{6}$= |
| $\frac{9}{10}$×$\frac{5}{7}$= | $\frac{2}{5}$+$\frac{1}{2}$= | $\frac{9}{10}$-$\frac{2}{5}$= | $\frac{3}{4}$+$\frac{2}{3}$= |
| 14×$\frac{2}{21}$= | $\frac{2}{5}$×$\frac{1}{6}$= | $\frac{5}{12}$÷$\frac{5}{6}$= | $\frac{4}{9}$-$\frac{1}{3}$= |
2．下面各组数中互为倒数的是（ ）
0 158635 158643 158649 158653 158659 158661 158665 158671 158673 158679 158685 158689 158691 158695 158701 158703 158709 158713 158715 158719 158721 158725 158727 158729 158730 158731 158733 158734 158735 158737 158739 158743 158745 158749 158751 158755 158761 158763 158769 158773 158775 158779 158785 158791 158793 158799 158803 158805 158811 158815 158821 158829 199269
| A． | 0.5和2 | B． | $\frac{1}{8}$和 $\frac{7}{8}$ | C． | $\frac{4}{3}$和 $\frac{1}{3}$ |