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Bài 2: Tính nhanh
a) 29 + 132 + 237 + 868 + 3
= 29+(132+858)+(237+3)
=29+990+240
=1259
2 . 53 . 27 + 6 . 9 . 87 - 3 . 18 . 40
= 2. 53 . 9 . 3 + 2. 3 .9 .87 - 3 .2 .9 .40
= 54.53+54.87-54.40
=54(53+87-40)
=54. 100=5400
12 . 25 + 29 . 25 + 59 . 25
= 25 . ( 12+29+59)
=25 . 90
=2250
43 . 37 + 93 . 43 + 57 . 61 + 69 . 57
= 43.(37+93)+57(61+69)
=43.130+57.130
=130.(43+57)
=130.100
=13 000
12 . 53 + 53 . 172 - 53
=53(12+172-1)
=53.184
=9752
35 . 54 + 35 . 58 + 65 . 75 + 65 . 45
=35(54+58)+65(75+45)
=35.112+65.120
=3920+7800
=11720
39 . 8 + 70 . 3 + 31 . 8
=8(39+31)+70.3
=8.70+70.3
=70.(8+3)
=70.11
=770
a, 39 . 8 + 60 . 2 + 21 . 8
= 39 . 8 + 15 . 4 . 2 + 21 . 8
= 39 . 8 + 15 . 8 + 21 . 8
= 8 . ( 39 + 15 + 21 )
= 8 . 75
= 600
b, 12 . 53 + 53 . 172 - 53 . 84
= 53 . ( 12 + 172 - 84 )
= 53 . 100
= 5300
c, 35 . 34 + 35 . 86 + 65 . 75 + 65. 67 + 65.45
= 35 . ( 34 + 86 ) + 65 . ( 75 + 67 + 45 )
= 35 . 120 + 65 . 187
= 4200 + 12155
= 16355
d, 36 . 28 + 36 . 82 + 64 . 69 + 64 . 41
= 36 . ( 28 + 82 ) + 64 . ( 69 + 41 )
= 36 . 110 + 64 . 110
= 110 . ( 36 + 64 )
= 110 . 100
= 11000
a, 39 . 8 + 60 . 2 + 21 . 8
= 39 . 8 + 15 . 4 . 2 + 21 . 8
= 39 . 8 + 15 . 8 + 21 . 8
= 8 . ( 39 + 15 + 21 )
= 8 . 75
= 600
b, 12 . 53 + 53 . 172 - 53 . 84
= 53 . ( 12 + 172 - 84 )
= 53 . 100
= 5300
c, 35 . 34 + 35 . 86 + 65 . 75 + 65. 67 + 65.45
= 35 . ( 34 + 86 ) + 65 . ( 75 + 67 + 45 )
= 35 . 120 + 65 . 187
= 4200 + 12155
= 16355
d, 36 . 28 + 36 . 82 + 64 . 69 + 64 . 41
= 36 . ( 28 + 82 ) + 64 . ( 69 + 41 )
= 36 . 110 + 64 . 110
= 110 . ( 36 + 64 )
= 110 . 100
= 11000
A.35 x 34 + 35 x 38 + 65 x 75 + 65 x 45
Câu này không tính hợp lí được
B. 12x 53 + 53 x 172 - 53 x 84
= 53 x (12 + 172 - 84)
= 53 x 100
= 5300
C. 36 x 28 + 36 x 82 + 64 x 69 + 64 x 41
= 36 x (28+82) + 64 x (69+41)
= 36 x 110 + 64 x 110
= (36+64) x 110
= 100 x 110
= 11 000
D. A = 1+2+3+...+100
= (1+ 100) x 50
= 101 x 50
= 5050
E. B =17+19+...+101+103
= (103 +17) x [(103 - 17):2 + 1]
= 120 x 44
=5280
G. D= 3x (12+13+14+15) + 3x(8+7+6+5)
= 3 x (5+6+7+8+12+13+14+15)
= 3 x (20 x 4)
= 3 x 80
=240
A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72
A = 78 x ( 31 + 24 + 17 ) + 22 x 72
A = 78 x 72 + 22 x 72
A = 72 x ( 78 + 22 )
A = 72 x 100
A = 7200
C = 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
C = 39 x ( 53 + 47 ) - 21 x ( 53 - 47 )
C = 39 x 100 - 21 x 6
C = 3900 - 126
C = 3774
a, 35.(34+86) + 65.(75+45)
=35.120 + 65.120
=120.(35+65)
=120. 100
=12000
a) 35 * 34 + 35 * 86 + 65 * 75 + 65 * 45
= 35 x ( 34 + 86 ) x 65 x ( 75 + 45 )
= 35 x 120 x 65 x 120
= 120 x ( 35 + 65 )
= 120 x 100
= 12000
a) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= 35 x ( 34 + 86 ) + 65 x ( 75 + 45 )
= 35 x 120 + 65 x 120
= 120 x ( 35 + 65 )
= 120 x 100
= 12 000
\(a,=35.\left(34+86\right)+65.\left(75+45\right)\)
\(=35.120+65.120=120.\left(35+65\right)=120.100=12000\)
\(b,=24.25+24.37+24.38=24.\left(25+37+38\right)=24.100=2400\)
a, = 35.(34+86) +65.(75+45) b, = 53.( 12+172-84)
= 35.120+65.120 = 53. 100= 5300
= 120.(35+65)
=120.100
= 12000