1033. Выполните умножение: 1)-12.5; 2)-0,4 · 1,5; 3) 3,4 · (-1,8); 4)-3/4 · (-5/6); 5) -15/16 · (-48/55); 6) -13/24 · 16/39; 7) 6/35 · (-14/15); 8) -7/12 · 24; 9) 45 · (-8/15); 10) 16/17 · (-6/8); 11) -3 5/9 · (-5 1/4); 12)-1 5/7 · 6 1/8; 1034. Выполните умножение: 1) 16 · (-3); 2) -8 · (-7); 5) -4/7 · 7/9; 6) -6 · (-5/24);

1) -12.5

Преобразуем десятичную дробь в обыкновенную: -12.5 = -12 5/10 = -12 1/2 = -25/2

-25/2 = -12,5

2) -0,4 ⋅ 1,5

Преобразуем десятичные дроби в обыкновенные: -0,4 = -4/10 = -2/5; 1,5 = 1 5/10 = 1 1/2 = 3/2

-2/5 ⋅ 3/2 = - (2⋅3) / (5⋅2) = - (1⋅3) / (5⋅1) = -3/5 = -0,6

3) 3,4 ⋅ (-1,8)

Преобразуем десятичные дроби в обыкновенные: 3,4 = 3 4/10 = 3 2/5 = 17/5; -1,8 = -1 8/10 = -1 4/5 = -9/5

17/5 ⋅ (-9/5) = - (17⋅9) / (5⋅5) = -153/25 = -6,12

4) -3/4 ⋅ (-5/6)

-3/4 ⋅ (-5/6) = (3⋅5) / (4⋅6) = (1⋅5) / (4⋅2) = 5/8 = 0,625

5) -15/16 ⋅ (-48/55)

-15/16 ⋅ (-48/55) = (15⋅48) / (16⋅55) = (3⋅3) / (1⋅11) = 9/11

6) -13/24 ⋅ 16/39

-13/24 ⋅ 16/39 = - (13⋅16) / (24⋅39) = - (1⋅2) / (3⋅3) = -2/9

7) 6/35 ⋅ (-14/15)

6/35 ⋅ (-14/15) = - (6⋅14) / (35⋅15) = - (2⋅2) / (5⋅5) = -4/25 = -0,16

8) -7/12 ⋅ 24

-7/12 ⋅ 24 = - (7⋅24) / 12 = - (7⋅2) / 1 = -14/1 = -14

9) 45 ⋅ (-8/15)

45 ⋅ (-8/15) = - (45⋅8) / 15 = - (3⋅8) / 1 = -24/1 = -24

10) 16/17 ⋅ (-6/8)

16/17 ⋅ (-6/8) = - (16⋅6) / (17⋅8) = - (2⋅6) / (17⋅1) = -12/17

11) -3 5/9 ⋅ (-5 1/4)

Преобразуем смешанные дроби в неправильные: -3 5/9 = -32/9; -5 1/4 = -21/4

-32/9 ⋅ (-21/4) = (32⋅21) / (9⋅4) = (8⋅7) / (3⋅1) = 56/3 = 18 2/3

12) -1 5/7 ⋅ 6 1/8

Преобразуем смешанные дроби в неправильные: -1 5/7 = -12/7; 6 1/8 = 49/8

-12/7 ⋅ 49/8 = - (12⋅49) / (7⋅8) = - (3⋅7) / (1⋅2) = -21/2 = -10,5

1) 16 ⋅ (-3)

16 ⋅ (-3) = -48

2) -8 ⋅ (-7)

-8 ⋅ (-7) = 56

5) -4/7 ⋅ 7/9

-4/7 ⋅ 7/9 = - (4⋅7) / (7⋅9) = - (4⋅1) / (1⋅9) = -4/9

6) -6 ⋅ (-5/24)

-6 ⋅ (-5/24) = (6⋅5) / 24 = (1⋅5) / 4 = 5/4 = 1,25