54. Выполните умножение или деление.

Решение:

1. \( -6,2 \cdot 1,9 \)

\( -6,2 \times 1,9 = -11,78 \)

2. \( -25,65 : (-3,42) \)

\( -25,65 : (-3,42) = 7,5 \)

3. \( 0,87 \cdot (-25) \)

\( 0,87 \times (-25) = -21,75 \)

4. \( -3,5 \cdot (-0,65) \)

\( -3,5 \times (-0,65) = 2,275 \)

5. \( 14,31 : 5,3 \)

\( 14,31 : 5,3 = 2,7 \)

6. \( -\frac{3}{14} \cdot 0,2 \)

\( -\frac{3}{14} \times \frac{2}{10} = -\frac{6}{140} = -\frac{3}{70} \)

7. \( -0,4 : \left( -\frac{8}{11} \right) \)

\( -0,4 : \left( -\frac{8}{11} \right) = -\frac{4}{10} : \left( -\frac{8}{11} \right) = -\frac{4}{10} \times \left( -\frac{11}{8} \right) = \frac{44}{80} = \frac{11}{20} \)

8. \( \frac{7}{8} : 63 \)

\( \frac{7}{8} : 63 = \frac{7}{8 \times 63} = \frac{1}{8 \times 9} = \frac{1}{72} \)

9. \( -2\frac{2}{9} : \frac{35}{81} \)

\( -2\frac{2}{9} = -\frac{20}{9} \). \( -\frac{20}{9} : \frac{35}{81} = -\frac{20}{9} \times \frac{81}{35} = -\frac{20 \times 81}{9 \times 35} = -\frac{4 \times 9}{1 \times 7} = -\frac{36}{7} \)

10. \( -27,81 : 2,7 \)

\( -27,81 : 2,7 = -10,3 \)

11. \( \frac{7}{8} \cdot \left( -\frac{7}{8} \right) \)

\( \frac{7}{8} \times \left( -\frac{7}{8} \right) = -\frac{49}{64} \)

12. \( -\frac{2}{5} : 20 \)

\( -\frac{2}{5} : 20 = -\frac{2}{5 \times 20} = -\frac{2}{100} = -\frac{1}{50} \)

13. \( -3\frac{2}{7} \cdot 14 \)

\( -3\frac{2}{7} = -\frac{23}{7} \). \( -\frac{23}{7} \times 14 = -23 \times 2 = -46 \)

14. \( -2,8 \cdot 1,1 \)

\( -2,8 \times 1,1 = -3,08 \)

15. \( -3,9 : (-0,13) \)

\( -3,9 : (-0,13) = 30 \)

16. \( 9,72 : (-8,1) \)

\( 9,72 : (-8,1) = -1,2 \)

17. \( -\frac{4}{9} \cdot \frac{3}{8} \)

\( -\frac{4}{9} \times \frac{3}{8} = -\frac{12}{72} = -\frac{1}{6} \)

18. \( -\frac{1}{3} \cdot \frac{4}{9} \)

\( -\frac{1}{3} \times \frac{4}{9} = -\frac{4}{27} \)

Ответ: -11,78; 7,5; -21,75; 2,275; 2,7; -3/70; 11/20; 1/72; -36/7; -10,3; -49/64; -1/50; -46; -3,08; 30; -1,2; -1/6; -4/27.