a) 491 x (267+53) - 491 x ( 153 + 67 )

=491x<(267+53) - (153+67)>

=491x<300-200>

=491x100

=49100

b) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21 

=53x(39-21) - 47x(39-21)

=53x18-47x18

=18x(53-47)

=18x6

=108

bạn ơi cho mình sửa phần b) nha

b) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21 

=53x(39-21) + 47x(39-21)

=53x18+47x18

=18x(53+47)

=18x100

=1800

không trả lời linh tinh

= a) 93.85+17.45-170 

Áp dụng các tính chất 

=491.267+491.53-491.153+491.67

=491.(267+153)-491.(53+67)

=491.420-491.120

=491.(420-120)

=491.300

=147300

45.48-90.24+145

=(45.2).(48:2)-90.24+145

=90.24-90.24+145

=0+145

=145

754.75-2262.25+4568

=754.75-(2262:3).(25.3)+4568

=754.75-754.75+4568

=0+4568

=4568

23.157+15.46-23.87

=23.(147-87)+15.46

=23.60+15.46

=23.60+(15.2).(46:2)

=23.60+50.23

=23.(60+50)

=23.110

=2530

a) 93.85+17.45-170=8500

b) 491.(267+53) -491. (153+67) =49100

c) 45.48-90.24+145=145

d) 754.75-2262.25+4568=4568

e) 23.157+15.46 -23.87=2300

491.(267+53) + 491.(151+67) = 491.(267+53+151+67)

                                                = 491 . 538

                                                = 264158

a)

$37+41+117+159+62$

$=(37+159)+(41+117)+62$

$=196+158+62$

$=416$

b)

$73+86+968+914+3032$

$=(968+3032)+(86+914)+73$

$=4000+1000+73$

$=5073$

a)38 + 41 + 117 + 159 + 62 

= ( 38 + 62 ) + ( 41 + 159 ) + 117

= 100 + 200 + 117

= 300 + 117 = 417

b)73 + 86 + 968 + 914 + 3032

= ( 968 + 3032 ) + ( 86 + 914 ) + 73

= 4000 + 1000 + 73

= 5000 + 73 = 5073

c)341 . 67 + 341 . 16 + 659 . 83 

= 341 .  ( 67 + 16 ) + 659 . 83

= 341 . 83 + 659 . 83

= 83 . ( 341 + 659 )

= 83 . 1000

= 83000

d)42 . 53 + 47 . 156 - 47 . 114  

= 42 . 53 + 47 . ( 156 - 114 )

= 42 . 53 + 47 . 42

= 42 . ( 53 + 47 )

= 42 . 100

= 4200

e)563 . 23 + 23 . 36 + 23

= 23 . ( 563 + 36 + 1 )

= 23 . 600

= 13800

f)132 + 157 + 43 + 68

= ( 132 + 68 )  + ( 157 + 43 )

= 200 + 200

= 400

g)49 . 68 + 100 . 34 + 68

= 49 . 68 + 50. 2 . 34 + 68

= 49. 68 + 50 . 68 + 68

= 68 . ( 49 + 50 + 1 )

= 68 . 100

= 6800

h)491 . (267 + 53) - 491 . (153 + 67)

= 491 . 267 + 491 . 53 - 491 . 153 - 491 . 67

= 491 . ( 267 + 53 - 153 - 67 )

= 491 . 100

= 49100

Trả lời:

a) 38 + 41 + 117 + 159 + 62 = ( 38 + 62 ) + ( 41 + 159 ) + 117 = 100 + 200 + 117 = 417

b) 73 + 86 + 968 + 914 + 3032 = 73 + ( 86 + 914 ) + ( 968 + 3032 ) = 73 + 1000 + 4000 = 5073

c) 341 . 67 + 341 . 16 + 659 . 83 = 341 . ( 67 + 16 ) + 659 . 83 = 341 . 83 + 659 . 83 = 83 . ( 341 + 659 ) = 83 . 1000 = 83000    

d) 42 . 53 + 47 . 156 - 47 . 114 = 42 . 53 + 47 . ( 156 - 114 ) = 42 . 53 + 47 . 42 = 42 . ( 53 + 47 ) = 42 . 100 = 4200         

e) 563 . 23 + 23 . 36 + 23 = 23 . ( 563 + 36 + 1 ) = 23 . 600 = 13800

f) 132 + 157 + 43 + 68 = ( 132 + 68 ) + ( 157 + 43 ) = 200 + 200 = 400

g) 49 . 68 + 100 . 34 + 68 = 49 . 68 + 50 . 2 . 34 + 68 = 49 . 68 + 50 . 68 + 68 = 68 . ( 49 + 50 + 1 ) = 68 . 100 = 6800

h) 491 . (267 + 53) - 491 . (153 + 67) = 491 . [ ( 267 + 53 ) - (153 + 67 ) ] = 491 . ( 267 + 53 - 153 - 67 ) = 491 . 100 = 49100

Bài 1:

a: 212+109+188

=212+188+109

=400+109

=509

b: 305+295+140

=600+140

=740

c: \(9\cdot4\cdot25\cdot8\cdot125\)

\(=9\cdot100\cdot1000\)

=900000

d: 35+56+65+44

=35+65+56+44

=100+100

=200

e: 277+194+206+123

=277+123+194+206

=400+400

=800

g: \(8\cdot25\cdot2\cdot4\cdot5\cdot125\)

\(=2\cdot5\cdot4\cdot25\cdot8\cdot125\)

\(=10\cdot100\cdot1000=1000000\)

h: \(29\cdot25+29\cdot45+29\cdot30\)

\(=29\left(25+45+30\right)=29\cdot100=2900\)

i: \(36\left(143+57\right)+64\left(143+57\right)\)

\(=36\cdot200+64\cdot200\)

\(=200\left(36+64\right)=200\cdot100=20000\)

k: \(491\cdot\left(747+53\right)+491\left(153+47\right)\)

\(=491\left(747+153+53+47\right)\)

\(=491\left(900+100\right)=491\cdot1000=491000\)

Bài 4:

a: M=1+2+3+...+103

\(=\frac{103\left(103+1\right)}{2}=103\cdot\frac{104}{2}=103\cdot52=5356\)

b: Số số hạng của dãy là (99-3):4+1=96:4+1=24+1=25(số)

Tổng của dãy số là:

\(N=\left(99+3\right)\cdot\frac{25}{2}=51\cdot25=1275\)

c: Số số hạng của dãy là:

(991-1):10+1=990:10+1=99+1=100(số)

Tổng của dãy số là:

\(C=\left(991+1\right)\cdot\frac{100}{2}=992\cdot50=49600\)

=-491-205+491=-205

= - 491 - 205 + 491 = -205