\(0,5\times40\times0,2\times20\times0,25\)

\(=\left(0,5\times0,2\right)\times\left(40\times20\times0,25\right)\)

\(=0,1\times200\)

\(=20\)

~ Hok tốt ~

#)Trả lời :

c) ( 67,895 x 0,5 + 3,1416 x 0,5 ) x ( 9 x 0,9 + 0,9 - 0,9 x 10 )

= ( 67,895 x 0,5 + 3,1416 x 0,5 ) x ( 8,1 + 0,9 - 9 ) 

= ( 67,895 x 0,5 + 3,1416 x 0,5 ) x ( 9 - 9 )

= ( 67,895 x 0,5 + 3,1416 x 0,5 ) x 0

= 0

      #~Will~be~Pens~#

Chọn B

B

a,

36 x 40 = (36 x 4) x 10 = 144 x 10 = 1 440

72 x 60 = (72 x 6) x 10 = 432 x 10 = 4 320

89 x 50 = (89 x 5) x 10 = 445 x 10 = 4 450

b,

450 x 70 = (45 x 7) x 100 = 315 x 100 = 31 500

2300 x 500 = (23 x 5) x 10 000 = 115 x 10 000 = 1 150 000

17 000 x 30 = (17 x 3) x 10 000 = 510 000

a) \(x-285\div35=5\times54\)

\(x-\dfrac{57}{7}=270\)

\(x=\dfrac{1947}{7}\)

b) \(\left(x+120\right)\div20=8\)

\(x+120=160\)

\(x=40\)

c) \(\left(x+5\right)\times3=300\)

\(x+5=100\)

\(x=95\)

d) \(\left(x+100\right)\times4=800\)

\(x+100=200\)

\(x=100\)

a) \(x-285:35=5x54\)

\(x-\dfrac{57}{7}=270\)

\(x=270+\dfrac{57}{7}=\dfrac{1890}{7}+\dfrac{57}{7}=\dfrac{1947}{7}\)

b) \(\left(x+20\right):20=8\)

\(\left(x+20\right)=8x20\)

\(x+20=160\)

\(x=160-20=140\)

c) \(\left(x+5\right)x3=300\)

\(x+5=300:3\)

\(x+5=100\)

\(x=100-5=95\)

d) \(\left(x+100\right)x4=800\)

\(x+100=800:4\)

\(x+100=200\)

\(x=200-100=100\)

a) x = 44.             

b) x = 40.            

c) x = 95.             

d) x = 10.

a) x - 120: 30 = 40

    x    -40        =40

              x        =40+40

              x        =80

b) (x + 120) : 20 = 8

    (x+ 120)         = 8x20

     x+120           =160

     x                   = 160-120

     x                  = 40

c) (x + 5). 3 = 300

     x+5=300:3

     x+5=100

     x=100-5

     x=95

d) x.2 + 21 : 3= 27

    x.2   +7=27

      x.2   = 27-7

    x.2= 20

      x=20:2

      x=10

a) 172 + 10 x 2 = 170 +20 = 192

b) 10 x 2 + 300 = 20 + 300 = 320

c) 69 – 54 : 6 = 69 – 9 = 60

d) 900 + 9 x 10 = 900 +90 = 990

e) 20 x 6 + 70 = 120 + 70 = 190

f) 72 + 300 x 3 = 72 + 900 = 972

a) 47 000 + 8 000 + 3 000 = (47 000 + 3 000) + 8 000

                                          = 50 000 + 8 000

                                          = 58 000

    250 000 – 5 x 10 000 = 250 000 – 50 000

                                   = 200 000

    20 x 3 x 5 x 7 = (3 x 7) x (20 x 5)

                           = 21 x 100

                           = 2 100

b) (3 075 – 75) : 3 = 3 000 : 3

                             = 1 000

    8 x (700 + 300) = 8 x 1 000

                             = 8 000

    92 x 753 – 82 x 753 = 753 x (92 – 82)  

                                     = 753 x 10

                                     = 7 530

`x-14 +x+54+x+20=300`

`=> (x+x+x)+(-14+54+20)=300`

`=>3x+60=300`

`=>3x=240`

`=>x=240:3`

`=>x=80`

Vậy `x=80`

` @ \color{yellow}{Le_mon}`

x = 80