a) S

b) Đ

c) Đ

d) S

Nếu đúng thì Kết bạn rồi k đúng cho mình nhé ;)

1x2x3x4x5x6x7x8x9

2x3x4x5x6x7x8x9x10

=1/10

b)1/2*2/3*3/4*4/5*5/6*6/7*7/8*8/9*9/10

=1x2x3x4x5x6x7x8x9

  2x3x4x5x6x7x8x9x10

= 1

  10

\(\dfrac{24}{9}+\dfrac{-a}{3}=\dfrac{36}{\dfrac{277}{5}}+\dfrac{-a}{4}=\dfrac{13}{20}\)

24/9 - a/3 = 36/27

           a/3 = 24/9 - 36/27

            a/3 =   4/3

vậy a là 4

`5/2 - 2/3 + 5/4`

`= 30/12 - 8/12 + 15/12`

`= (30-8+15)/12`

`= 37/12`

`----`

`20/12 + 36/18 -21/28`

`= 5/3 + 2-3/4`

`= 20/12 + 24/12 -9/12`

`= 35/12`

`5/2-2/3+5/4`

`=30/12-8/12+15/12`

`=37/12`

`20/12+36/18-21/28`

`=5/3+2-3/4`

`=20/12+24/12-9/12`

`=35/12`

\(\frac{4}{25}-\frac{5}{100}\)

\(=\frac{16}{100}-\frac{5}{100}\)

\(=\frac{16-5}{100}=\frac{11}{100}\)

\(\frac{63}{30}-\frac45\)

\(=\frac{21}{10}-\frac45\)

\(=\frac{21}{10}-\frac{8}{10}=\frac{21-8}{10}=\frac{13}{10}\)

\(\frac{17}{10}-\frac95=\frac{17}{10}-\frac{18}{10}=\frac{17-18}{10}=\frac{-1}{10}\)

\(\frac59-\frac{7}{36}=\frac{20}{36}-\frac{7}{36}=\frac{20-7}{36}=\frac{13}{36}\)

\(\frac{53}{16}-\frac34=\frac{53}{16}-\frac{12}{16}=\frac{53-12}{16}=\frac{41}{16}\)

\(\frac{36\times4+27}{36\times5-9}=\frac{36\times4+27}{36\times\left(4+1\right)-9}=\frac{36\times4+27}{36\times4+36-9}=\frac{36\times4+27}{36\times4+27}=1\)

sai rồi bạn ơi

   35  x 20 x 5           8 x 9 x 125         25 x 7 x 4    72:(8x3)

= 35 x ( 20  x5 )      = ( 8x125) x 9    = (25x4)x7    = 72: 24

= 35 x 100              = 1 000 x 9       = 100x7        = 3

= 3 500                  = 9  000            =700

(36x7):4

=36: 4 x 7 

= 9 x7

= 63 

35 x 20 x 5 = 35\(\times\)(20 \(\times\)5)= 35 \(\times\)100=3500

8 \(\times\)9 \(\times\) 125 =(8\(\times\) 125)\(\times\)9=1000\(\times\)9=9000

25 \(\times\)7\(\times\)4=(25 \(\times\)4)\(\times\)7=100\(\times\)7=700

72 : (8\(\times\)3)=72 : 8 x 3 =(72:8) x 3=9 x   3=27

(36 x 7) : 4 =36 x 7 : 4 =7 x (36 :4)=7 x 9=63