(20,1*20,2 + 28,3 *12,4 ) * (11*9 -900*0.1-9)

=(20,1 *20,2 +28,3 *12.4)*(99-90-9) 

=20,1* 20,2 +28,3 *12,4 )*0 

=0

20,2 x 67,3 + 33,7 x 20,2 - 20,2

=20,2x ( 67,3 + 33,7 -1)

=20,2x100

=202

20,2 x 67,3 + 33,7 x 20,2 - 20,2

=20,2x ( 67,3 + 33,7 -1)

=20,2x100

=202

AI BIẾT

Tính bằng cách thuận tiện nhất :

a. 36,4 x 99 + 36 + 0,4

=36,4 x 99 + 36,4

=36,4 x 99 + 36,4x1

=36,4x(99+1)

=36,4x100

=3640

b. 77,28 x 20,2 + 23,72 x 20,2 - 20,2

=77,28 x 20,2 + 23,72 x 20,2 - 20,2x1

=20,2x(77,28+23,72-1)

=20,2x100

=2020

a. 36,4 x 99 + 36 + 0,4

= 3603,6 + 36,4 

= 3640

b. 77,28 x 20,2 + 23,72 x 20,2 - 20,2

= 20,2 x ( 77,28  + 23,72 -1 )

= 20,2 x 100

= 2020

\(a,36,4\times99+36+0,4=\\ 36\times99+0,4\times99+36+0,4\\ =36\times\left(99+1\right)+0,4\times\left(99+1\right)\\ =36\times100+0,4\times100\\ =3600+40\\ =3640\\b,77,28\times20,2+23,72\times20,2-20,2\\ =\left(77,28+23,72-1\right)\times20,2\\ = 100\times20,2\\ =2020\)

0,3625

\(\text{0,29 x 8 x 1,25 = ?}\)

\(0.29X8=2.32\)

\(2.32X1.25=\text{2.9}\)

0,29 x 8 x 1,25 

= 0.29 x 10

 = 2,9 

`29 xx 20,22 + 15 xx 20,22 + 20,22 xx 44 + 24 xx 10,11`

`= 20,22 xx (29 + 15 + 44 + 12)`

`= 20,22 xx 100`

`= 2022`

C1 : 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 24 x 10,11

= 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 12 x (2 x 10,11)

= 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 12 x 20,22

= 20,22 x 100

= 2022

C2: 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 24 x 10,11

= 20,22 x ( 29 + 15 + 44 + 12 )

= 20,22 x 100

= 2022

( 4/9 + 7/9 -  2/9 ) x 19/24  = 1 x 19/24 = 19/24

\(=\dfrac{19}{24}\times\left(\dfrac{4}{9}+\dfrac{7}{9}-\dfrac{2}{9}\right)=\dfrac{19}{24}\times1=\dfrac{19}{24}\)

\(\dfrac{19}{24}\times\left(\dfrac{4}{9}+\dfrac{7}{9}-\dfrac{2}{9}\right)\)

\(=\dfrac{19}{24}\times1=\dfrac{19}{24}\)

\(20,22\times18,6+20,22\times0,394+40,4\times21\)

\(=20,22\times\left(18,6+0,394\right)+40,4\times21\)

\(\approx384,06+848,4=1232,46\)

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