1
6–2+1=5 6-2=4 4+1=5 2
6 – (2 + 1) = 5 (2+1)= 3 6-3 = 3 3
2 + 3 x 5= 25 3X5= 15 2+15 = 17 4
9-2 x (3+1)= 1 (3+1)= 4 2x4 = 8 9-8 = 8
5
1475 + 1001 = 2476 1475 + (1000+1) = 2476 6
7
856 + 999 = 1855 856 +(+1000+1) = 1855 8
9
1600 - 1001 = 599 1600 - (1000-1) = 599 10
11
1600 - 999 = 601 1600 - (1000+1) = 601 12
13
60 20 = 3 400 200 = 2 16000 8000 = 2 14
2/3 de 30 = 20 2 x 30 = 60 60 3 = 20 15
47 + 28 = 75 Aproximo a 50 (sobran 3 y a単ado decena)
Aproximo a 30 ( sobran 2)
47 + 28 = 75 16
61 + 37 = 98 60 + 30 = 90 1+7=8 17
74 - 28 = 46 74 - 30 = 44 44 + 2 = 46 18
74 - 23 = 51 74 - 20 = 54 54 - 3 = 51 19
47 x 2 = 94 40 x 2 = 80 7 x 2 = 14 80 + 14 = 94
20
46 x 5 =230 46 x 10 =460 460 2 = 230 21
18 x 11 = 198 18 x 10 = 180 180 + 18 = 198 22
12 x 9 = 108 12 x 10 = 120 120 - 12 = 108 23
35 x 101 = 3535 35 x 100 = 3500 3500 + 35 = 3535 24
27 x 99 = 2673 27 x 100 = 2700 2700 - 27 = 2673 25
3,8 + 2,1 = 5,9 4 + 2 = 6 (aproximado) 26
5,2 - 2,7 = 2,5 5 + 2 = 3(aproximado) 27
3,89 + 12= 15,89 3 + 12= 15 28
8,59 – 4 = 4,59 8 - 4= 4 29
3,8 x 7 = 26,6 4 x 7 = 28(aproximado) 30
0,3 x 4 = 1,2 3 x 4 = 12 31
10% de 82 82 / 10 = 8,2 32
3% de 9 = 0,27 3 x 9 = 27 27 100 = 0,27 33