Пошаговое объяснение:

№55

1)

1/4 + 2/3 + 3/4 + 3/5 = (1/4 + 3/4) + (2/3 + 3/5) =

4/4 + (10/15 + 9/15) = 1 + 19/15 = 1 + 1 4//15 = 2 4/15

2)

4/5 + 1/3 + 2/3 + 3/5 = (4/5 + 3/5) + (1/3 + 2/3) =

7/5 + 3/3 = 1 2/5 + 1 = 2 2/5

3)

2 4/7 + 1 2/9 + 3 4/11 + 4 3/7 =

(2 4/7 + 4 3/7) + (1 2/9 + 3 4/11) =

6 7/7 + (1 22/99 + 3 36/99) =

7 + 4 58/99 = 11 58/99

№56

1) 0,2 + 1/7 = 2/10 + 1/7 = 14/70 + 10/70 = 24/70 = 12/35

2) 7/16 - 0,12 = 7/16 - 12/100 = 700/1600 - 192/1600 = 508/1600 = 127/400

3) 4,85 - 2 13/24 = 4 85/100 - 2 13/24 = 4 2040/2400 - 2 1300/2400 = 2 740/2400 = 2 37/120

4) 7 8/21 - 4 375/1000 = 7 8/21 - 4 3/8 = 7 64/168 - 4 63/168 = 3 1/168

№57

1) 1 : 5 = 1/5 (часть) - поля вспахивает за 1 час 1 тракторист

2) 1 : 8 = 1/8 (часть) - поля вспахивает за 1 час 2 тракторист

3) 1/5 + 1/8 = 8/40 + 5/40 = 13/40 (часть) - поля вспахивают за 1 час два тракториста работая вместе

Ответ:

Пошаговое объяснение:

№58

1)

6 7/8 -3 1/3 + 5 5/16 =6 42/48 - 3 16/48 + 5 15/48 = 8 41/48

2)

5 9/14 - 2 3/7 + 6,7 = 5 9/14 - 2 3/7 + 6 7/10 = 5 45/70- 2 30/70 + 6 49/70 =

= 9 64/70 = 9 32/35

3)

(15 5/6 - 9 25/27) -2 17/18 = (15 45/54 - 9 50/54) - 2 51/54 =

= (14 99/54 - 9 50/54) - 2 51/54 = 5 49/54 - 2 51/54 = 4 103/54 - 2 51/54 =

= 2 52/54 = 2 26/27

4)

(18 - 10 5/9) - ( 6 1/8 - 3 2/3) = (17 9/9 -10 5/9) - ( 6 3/24 - 3 16/24) =

= 7 4/9 - (5 27/24 - 3 16/24)= 7 4/9 - 2 9/24 = 7 4/9 - 2 3/8 =

= 7 32/72 - 2 27/72 = 5 5/72