3,2 + 4,65 : 1,5 

=3,2+3,1

=6,3

347 + 418 + 123 + 12

=(347+123)+(418+12)

=470+430

=900

34 x 35 + 35 x 38 + 65 x 40 + 65 x 32

=35*(34+38)+65*(32+40)

=35*72+65*72

=72*(35+65)

=72*100

=7200

19 x 16 x 4 + 76 x 34

=76*16+76*34

=76*(16+34)

=76*50

=3800

136 x 68 + 16 x2 x 136 

=136*68+32*136

=136*(68+32)

=136*100

=13600

125 x 25 + 125 x 74 + 125

=125*(25+74+1)

=125*100

=12500

Tính bằng cách thuận tiện hả

3,2 + 4,65 : 1,5 = 3,2 + 3,1 = 6,3

347 + 418 + 123 + 12 = (347 + 123) + (418 + 12) = 470 + 430 = 900

34 x 35 + 35 x 38 + 65 x 40 + 65 x 32 = 35 x ( 34 + 38) + 65 x (40 + 32) = 35 x 72 + 65 x 72 = 72 x (35 + 65) = 72 x 100 = 7200

19 x 16 x 4 + 76 x 34

136 x 68 + 16 x2 x 136 

125 x 25 + 125 x 74 + 125

1 : Tính nhanh:

a) 2376 + 3425 - 376 - 425 = ( 2376 - 376 ) + ( 3425 - 425 )

                                       = 2000 + 3000

                                       = 5000

b)4638 - 2437 + 5362 - 7563 = 2210 + ( - 2210 )

                                          = 0

c) 45 + 45 + 45 + 45 + 15 + 15 + 15 + 15

  = 45 x 4 + 15 x 4

 = ( 45 + 15 ) x 4

 = 60 x 4

 = 240

d) 4 x 125 x 25 x 8 = ( 4 x 25 ) x ( 125 x 8 )

                            = 100 x 1000

                            = 100000

e) 2 x 8 x 50 x 25 x 125 = ( 2 x 50 ) x ( 8 x 125 ) x 25

                                   = 100 x 1000 x 25

                                   = 100000 x 25

                                   = 2500000

2 : Tính nhanh bằng 2 cách:

C1 : 125 + 125 + 125 + 125 - 25 - 25 - 25 - 25

    = ( 125 - 25 ) + ( 125 - 25) + ( 125 - 25 ) + ( 125 - 25 )

    =100 + 100 + 100 + 100 

    = 100 x 4 

    = 400

C2 : 125 + 125 + 125 + 125 - 25 - 25 - 25 - 25

     = 125 x 4 - 25 x 4

     = ( 125 - 25 ) x 4

     = 100 x 4

     = 400

1.

a. 5000
b. 0

c. 240

d. 100000

e. 2500000

2.

400

1: Tính nhanh:

a, 2376 + 3425 - 376 - 425

 = ( 2376 - 376 ) + ( 3425 - 425 )

 = 2000 + 3000

 = 5000.

b, 4638 - 2437 + 5362 - 7563

 = 2210 + (-2210)

 = 0.

c, 45 + 45 + 45 + 45 + 15 + 15 + 15 + 15 + 15

 = ( 45 + 15 ) +  ( 45 + 15 ) +  ( 45 + 15 ) +  ( 45 + 15 ) 

 = 60 + 60 + 60 + 60

 = 240.

d, 4 x 125 x 25 x 8 

 = ( 4 x 25 ) x ( 125 x 8 )

 = 100 x 1000

 = 100000.

e, 2 x 8 x 50 x 25 x 125

 = ( 2 x 50 ) x ( 8 x 125 ) x 25

 = 100 x 1000 x 25

 = 2500000.

2: Tính nhanh bằng hai cách:

  125 + 125 + 125 + 125 - 25 - 25 - 25- 25

= ( 125 - 25 ) + ( 125 - 25 ) + ( 125 - 25 ) + ( 125 -25 )

= 100 + 100 + 100 + 100

= 400.

a) 135 . (-27) + 27 . 235

= 27 . (235 - 135)

= 27 . 100

= 2700

b) 36 . (-125) - 125 . (-46)

= 125 . (-36 + 46)

= 125 . 10

= 1250

c) 32 . (-64) - 64 . 68

= 64.(-32 - 68)

= 64.(-100)

= -6400

d) (145 - 45) . (-31) + 31 . (-100)

= 100 . (-31) + 31.(-100)

= 100.(-31 - 31)

= 100.(-62)

= -6200

a)

=(-135)x27+27x235

=27x[+(235+135)]

=27x31725

=856575

b)

=(-36)x125-125x(-46)

=125x[-(36+46)]

=125x(-1656)

=-207000

c)

=(-32)x64-64x68

=64x[-(68-32)]

=64x(-36)

=-(64x36)

=-2304

d)

=100x(-31)+31x(-100)

=(-100)x31+31x(-100)

=31x[-(100+100)]

=31x(-200)

=-(31x200)

=-6200

chúc học tốt nhớ tích cho tui nha

nếu tui đúng chứ tui cũng hông có chắc nữa

Bài 2:

a: \(17-x=3\)

=>\(x=17-3\)

=>x=14(nhận)

b: \(2\cdot\left(x-1\right):3=6\)

=>\(2\left(x-1\right)=6\cdot3=18\)

=>x-1=18/2=9

=>x=9+1=10(nhận)

c: \(x+\left(-2\right)=\left(-11\right)+7\)

=>\(x-2=-4\)

=>\(x=-4+2=-2\left(loại\right)\)

d: \(\left(x-1\right)^2-5=20\)

=>\(\left(x-1\right)^2=25\)

=>\(\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\left(nhận\right)\\x=-4\left(loại\right)\end{matrix}\right.\)

Câu 3:

a: Đặt *=a

\(\overline{57a3}⋮9\)

=>\(5+7+a+3⋮9\)

=>\(a+15⋮3\)

mà 0<=a<=9

nên a=3

=>*=a

b: \(A=123\cdot7+8+9\)

123*7 là số lẻ

9 là số lẻ

=>123*7+9 chia hết cho 2

mà 8 chia hết cho 2

nên \(A=123\cdot7+9+8⋮2\)

\(123\cdot7⋮3;9⋮3;8⋮̸3\)

=>\(A=123\cdot7+9+8⋮̸3\)

c: \(B=3\cdot5\cdot7+10^{50}\)

\(=5\cdot3\cdot7+5\cdot5^{49}\cdot2^{49}\)

\(=5\left(3\cdot7+5^{49}\cdot2^{49}\right)⋮5\)

=>B là hợp số

\(46\cdot99\)

\(=46\cdot\left(100-1\right)\)

\(=46\cdot100-46\)

\(=4600-46\)

\(=4554\)

___________

\(34\cdot11\)

\(=34\cdot\left(10+1\right)\)

\(=34\cdot10+34\)

\(=340+34\)

\(=374\)

___________

\(25\cdot12\) 

\(=5\cdot5\cdot12\)

\(=5\cdot60\)

\(=300\)

__________

\(15\cdot4\)

\(=15\cdot2\cdot2\)

\(=30\cdot2\)

\(=60\)

____________

\(45\cdot6\)

\(=45\cdot2\cdot3\)

\(=90\cdot3\)

\(=2700\)

________

\(13\cdot99\)

\(=13\cdot\left(100-1\right)\)

\(=13\cdot100-13\)

\(=1300-13\)

\(=1287\)

______________

\(16\cdot19\)

\(=16\cdot\left(20-1\right)\)

\(=16\cdot20-16\)

\(=320-16\)

\(=304\)

_____________

\(35\cdot98\)

\(=35\cdot\left(100-2\right)\)

\(=35\cdot100-35\cdot2\)

\(=3500-70\)

\(=3430\)

____________

\(125\cdot16\)

\(=125\cdot8\cdot2\)

\(=1000\cdot2\)

\(=2000\)

___________

\(47\cdot101\)

\(=47\cdot\left(100+1\right)\)

\(=47\cdot100+47\)

\(=4700+47\)

\(=4747\)

46 x 99 =4554  , 34 x 11 = 374 , 25 x 12 =- 300 , 15 x 4 = 60 , 45 x 6 = 270 , 13 x 99 = 1287 , 16 x 19 = 304

35 x 98 = 3430 , 125 x 16  = 2000 ,  47 x 101  = 4747

Bài 3 .

a.25.(-70).2.(-4)

=[25.(-4)].[(-70).2]

=(-100).(-140)

=14000

b.16.(12-6)-12.(16-6)

=(16.12-16.6)-(12.16-12.6)

=16.12-16.6-12.16+12.6

=(16.12-12.16)-(16.6-12.6)

=0-6.(16-12)

=0-24=-24

c.125.(-24)+24.255

=24.[(-125)+255]

=24.100

=2400

d)25.(-55)+(-25).45

=25.[(-55)+(-45)]

=25.(-100)

=-2500

Bài 4

a.3x+18=3

3x =3-18

3x =-15

x =-15:3

x =-5

Vậy x=-5

b)\(4\left|x\right|=16\)

\(\left|x\right|\)=16:4

\(\left|x\right|\)=4

⇒\(\left[{}\begin{matrix}x=-4\\x=4\end{matrix}\right.\)

Vậy x∈{-4;4}

3)a)=(25.2).[(-70).(-4)]

=50.(-280)

=-14000

b)=16.6-12.10

=96-120

=-24

c)=-3000+6120

=3120

d)=1375+-1125

=250

4)a) 3x=3-18

3x=-15

x=-15:3

x=-5

b) \x\=16:4

\x\=4

suy ra x=4;-4

a: =1250:25=50

b: =234(45+55)+234=23400+234=23634

c: =1000x1000=1000000

Bài 1

a) \(5\times72\times10\times2=\left(5\times2\times10\right)\times72=100\times72=7200\) 

b) \(40\times125=5\times\left(8\times125\right)=5\times1000=5000\) 

c) \(16\times6\times25=4\times4\times6\times25=\left(4\times6\right)\times\left(4\times25\right)=24\times100=2400\) Bài 2:

a) \(24\times57+43\times24=24\times\left(57+43\right)=24\times100=2400\) 

b) \(12\times19+80\times12+12=12\times\left(19+80+1\right)=12\times100=1200\) 

c) \(\left(36\times15\times169\right)\div\left(5\times18\times13\right)\) 

 \(=\left(18\times2\times3\times5\times13\times13\right)\div\left(5\times18\times13\right)\) 

\(=\left(2\times3\times13\right)\times\left(18\times5\times13\right)\div\left(5\times18\times13\right)\) 

\(=2\times3\times13\)

\(=78\)

d) \(\left(44\times52\times60\right)\div\left(11\times13\times15\right)\) 

\(=\left(4\times11\times4\times13\times4\times15\right)\div\left(11\times13\times15\right)\)

\(=\left(4\times4\times4\right)\times\left(11\times13\times15\right)\div\left(11\times13\times15\right)\)

\(=4\times4\times4\)

\(=64\)

Bài 3:

a) \(x-280\div35=5\times54\) 

                \(x-8=270\) 

                      \(x=270+8\) 

                      \(x=278\) 

b) \(\left(x-280\right)\div35=54\div4\) 

    \(\left(x-280\right)\div35=\dfrac{27}{2}\) 

               \(x-280=\dfrac{27}{2}\times35\) 

                \(x-280=\dfrac{945}{2}\) 

                          \(x=\dfrac{945}{2}+280\) 

                          \(x=\dfrac{1505}{2}\) 

c) \(\left(x-128+20\right)\div192=0\) 

                 \(x-128+20=0\times192\) 

                \(x-128+20=0\) 

                        \(x-128=0-20\) 

                        \(x-128=-20\)

                                  \(x=-20+128\) 

                                 \(x=108\) 

d) \(4\times\left(x+200\right)=460+85\times4\) 

    \(4\times\left(x+200\right)=460+340\) 

    \(4\times\left(x+200\right)=800\) 

             \(x+200=800\div4\) 

             \(x+200=200\) 

                      \(x=200-200\) 

                      \(x=0\) 

Bài 4:

a) \(\dfrac{7}{12}-\dfrac{5}{12}=\dfrac{2}{12}=\dfrac{1}{6}\) 

b) \(\dfrac{8}{11}+\dfrac{19}{11}=\dfrac{27}{11}\) 

c) \(\dfrac{3}{8}+\dfrac{5}{12}=\dfrac{9}{24}+\dfrac{10}{24}=\dfrac{19}{24}\) 

d) \(\dfrac{3}{4}+\dfrac{7}{12}=\dfrac{9}{12}+\dfrac{7}{12}=\dfrac{16}{12}=\dfrac{4}{3}\) 

Bài 5:

a) \(x-\dfrac{6}{7}=\dfrac{5}{2}\) 

           \(x=\dfrac{5}{2}+\dfrac{6}{7}\) 

           \(x=\dfrac{47}{14}\) 

b) \(\dfrac{12}{7}\div x+\dfrac{2}{3}=\dfrac{7}{5}\) 

            \(\dfrac{12}{7}\div x=\dfrac{7}{5}-\dfrac{2}{3}\) 

             \(\dfrac{12}{7}\div x=\dfrac{11}{15}\) 

                       \(x=\dfrac{12}{7}\div\dfrac{11}{15}\) 

                        \(x=\dfrac{180}{77}\)