№1
а) 7 - 4 5/9 = (6 + 9/9) - 4 5/9 = 2 4/9
б) 4 3/10 + 1 5/12 = 4 18/60 + 1 25/60 = 5 43/60
в) 6 13/21 + 2 9/14 = 6 26/42 + 2 27/42 = 8 + 1 11/42 = 9 11/42
г) 5 1/6 - 3 3/4 = 5 2/12 - 3 9/12 = 1 5/12
№2.
1) 3 1/12 + 4 11/15 + 1 3/5 = 3 5/60 +4 44/60 + 1 36/60=
= 8 + 1 25/60 = 9 25/60 = 9 5/12 (т)
Ответ: 9 5/12 т пшеницы собрали с двух участков.
№3.
у + 4 7/10 = 5 8/15
у= 5 8/15 - 4 7/10 = 5 16/30 - 4 21/30
у= 25/30
у= 5/6
проверим:
5/6 + 4 7/10 = 5 8/15
25/30 + 4 21/30 = 5 8/15
4 + 1 16/30 = 5 8/15
5 16/30 = 5 8/15
5 8/15 = 5 8/15
2,65* (х-3,06)= 4,24
2,65х - 2,65 * 3,06 = 4,24
2,65х - 8,109 = 4,24
2,65х= 4,240 + 8,109
х= 12,349 :2,65
х=4,66
проверим:
2,65 * (4,66 - 3,06) = 4,24
2,65 * 1,6 = 4,24
4,24=4,24
№4.1
19/36 = 12/36 + 6/36 + 1/36
19/36 = 1/3 + 1/6 + 1/36
№4.2
21,4 - 5 1/2 - (16 2/3 - 6,6 ) =
= 21,4 - 5,5 - 16 2/3 + 6,6 =
= 22,5 - 16 2/3 = 22 1/2 - 16 2/3=
= 22 3/6 - 16 4/6 = 5 5/6
по действиям:
1) 16 2/3 - 6,6 = 16 2/3 - 6 3/5 = 16 10/15 - 6 9/15 = 10 1/15
2) 21,4 - 5 1/2 = 21,4 - 5,5 = 15,9
3) 15,9 - 10 1/15 = 15 27/30 - 10 2/30 = 5 25/30 = 5 5/6