Ta có: \(13\cdot\left(-47\right)-53\cdot13\)

\(=13\cdot\left(-47-53\right)\)

\(=13\cdot\left(-100\right)=-1300\)

Ta có: \(27\cdot\left(-67\right)+33\cdot\left(-27\right)\)

\(=27\cdot\left(-67\right)-33\cdot27\)

\(=27\left(-67-33\right)\)

\(=27\cdot\left(-100\right)=-2700\)

Ta có: \(-49\cdot65+36\cdot\left(-49\right)+49\)

\(=-49\cdot65+\left(-49\right)\cdot36+\left(-49\right)\cdot\left(-1\right)\)

\(=-49\cdot\left(65+36-1\right)\)

\(=-49\cdot100=-4900\)

Ta có: \(136\cdot\left(-47\right)+36\cdot47\)

\(=\left(-136\right)\cdot47+36\cdot47\)

\(=47\cdot\left(-136+36\right)\)

\(=47\cdot\left(-100\right)=-4700\)

Ta có: \(\left(-48\right)\cdot72+36\cdot\left(-304\right)\)

\(=-96\cdot36+36\cdot\left(-304\right)\)

\(=36\cdot\left(-96-304\right)\)

\(=36\cdot\left(-400\right)=-14400\)

a, 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

= 53 x (39-21) + 47 x (93-21)

=53 x 18 + 47 x 18

= (53 +47) x 18

=100 x 18

=1800

b,2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40

=24 x 53 + 24 x 87 - 24 x 40

=24 x (53+87-40)

=24 x 100

=2400

c,5 x 7 x 77 - 7 x 60 +49 x 25 -15 x 42.

=5 x 7 x 77 - 7 x 5 x 12 +49 x 5 x 5 - 5 x 3 x 42.

=5 x 539 - 84 x 5 +245 x 5 -5 x 126

=5 x (539 - 84 +245 -126)

=5 x 574

=2870

tính nhanh cơ

a, 53 x 39 + 47 x 39 ‐ 53 x 21 ‐ 47 x 21
= 53 x ﴾39‐21﴿ + 47 x ﴾93‐21﴿
=53 x 18 + 47 x 18
= ﴾53 +47﴿ x 18
=100 x 18
=1800
b,2 x 53 x 12 + 4 x 6 x 87 ‐ 3 x 8 x 40
=24 x 53 + 24 x 87 ‐ 24 x 40
=24 x ﴾53+87‐40﴿
=24 x 100
=2400
c,5 x 7 x 77 ‐ 7 x 60 +49 x 25 ‐15 x 42.
=5 x 7 x 77 ‐ 7 x 5 x 12 +49 x 5 x 5 ‐ 5 x 3 x 42.
=5 x 539 ‐ 84 x 5 +245 x 5 ‐5 x 126
=5 x ﴾539 ‐ 84 +245 ‐126﴿
=5 x 574
=2870

Mi Su

Bạn dùng tính chất phân phối, giao hoán để làm nhé

A+0   B=2400   c=420

1) a) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

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

= 39 x 100 - 21 x 6

= 3900 - 126

= 3774

b) 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40

= 1272 + 2088 - 960

= 3360 - 960

= 2400

c) 5 x 7 x 77 - 7 x 60 + 47 x 25 - 15 x 42

= 2695 - 420 + 1175 - 630

= 2275 + 545

= 2820

2) a) x : [(1800 + 600) : 30] = 560 : (315 - 35)

                     x : (2400 : 30) = 560 : 280

                                  x : 80 = 2

                                         x = 2 x 80

                                    => x = 160

b) [(250 - 25) : 15] : x = (450 - 60) : 130

                225 : 15 : x = 390 : 130

                         15 : x = 3

                               x  = 15 : 3

                           => x = 5

Học tốt!!!

a,102

b,2400

c,2870

a, 53 * 39 + 47 * 59 - 53 * 21 - 47 * 21     c, (4³ * 5^{2 -} 4³ ) : ( 4 * 4² ) 

= ( 53 + 47 ) *  39 - ( 53 + 47 ) * 21             = ( 64 * 25 - 64 ) : ( 4 * 16 )

= 100 * 39 - 100 * 21                                    = ( 1600 - 64 ) :  64

= ( 39 - 21 ) * 100                                         = 1536 : 64

= 18 * 100                                                     = 24

= 1800

Tính hợp lí:

a) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21.

b) 5 x 7 x 77- 7 x 60 + 49 x 25 - 15 x 42

c) ( 43 x 52 - 43 ) : ( 4 x 42 )

d) ( 2 + 5 + 11 +...+ 47 + 65

đ) ( 45 x 16 - 17 ) : ( 28 + 45 x 15 )

Đọc tiếp...

`16/27xx13/29+16/27xx14/29`

`=16/27xx(13/29+14/29)`

`=16/27xx27/29`

`=16/29`

`48/49+15/39-18/49+15/39`

`=(48/49-18/49)+(15/39+15/39)`

`=30/49+30/39`

`=880/637`

a ) x = 1 3 . b ) x = 22 15 . c ) x = 50 9 . d ) x = 5 19 .

X=(1800+600):30):560:(315:35)

X=(2400:30):560:9

X=80:560:9

X=80x1/560x1/9

X=1/7x1/9

X=1/63

A=58x72+63x81-58x52-63x61

  = (58x72-58x52)+(63x81-63x61)

  = 58(72-52)+63(81-61)

  = 58x20+63x20

  = 1160+1260

  = 2420

B=87x96-27x13+13x27-87x86

  = (87x96-87x86)-(27x13-13x27)

  = 87(96-86)-27(13-13)

  = 87x10 - 27x0

  = 870-0

  = 870

C= 53x39+87x39-53x31-47-21

  = (53x39+87x39)-(53x31+47+21)

  = 39(53+87)-(53x31+68)

  = 39x140 - 53x31 -68

  = 5460 - 1643 - 68

  = 3749