`(2/3xx4/5)xx5/6`

`=2/3xx4/5xx5/6`

`=2/3xx4/6`

`=2/3xx2/3`

`=1`

__

`(4/5+5/4)xx3/4`

`=(16/20+25/20)xx3/4`

`=41/20xx3/4`

`=123/80`

__

`27/12+17/6-25/36-15/6`

`=(27/12-25/36)+(17/6-15/6)`

`=(81/36-25/36)+2/6`

`=56/36+2/6`

`=56/36+12/36`

`=68/36`

`=17/9`

\(\dfrac{27}{86}\) < \(\dfrac{27}{81}\) = \(\dfrac{1}{3}\) = \(\dfrac{9}{27}\) < \(\dfrac{25}{27}\) 

Vậy \(\dfrac{27}{86}\) < \(\dfrac{25}{27}\) 

 \(\frac{21}{11}\times\frac{22}{17}\times\frac{68}{63}\)

=\(\frac{21}{1}\times\frac{2}{17}\times\frac{68}{63}\)

= 21 x \(\frac{8}{63}\)

=\(\frac{8}{3}\)

bạn tính cẩn thận thì sẽ ra bài này rất dễ

\(\frac{5}{15}+\frac{3}{15}+\frac{4}{20}+\frac{18}{27}+\frac{12}{16}+\frac{20}{25}\\ =\frac{1}{3}+\frac{1}{5}+\frac{1}{5}+\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\\ \)

\(=\left(\frac{1}{3}+\frac{2}{3}\right)+\left(\frac{1}{5}+\frac{1}{5}+\frac{4}{5}\right)+\frac{3}{4}\\ =1+\frac{5}{6}+\frac{3}{4}=2\frac{7}{12}=\frac{31}{12}\)

#Châu's ngốc

= (27/12 + 25/36)+(17/6 + 15/6)= 81/36 + 25/36 + 17/6 + 15/6 = 106/36 + 32/6 = 192/36 + 106/36 = 298/36 = 149/18

a) 19,17x25x4=19,17(25x4)=19,17x100=1917

b)1,79x(8x125)=1,79x1000=1790

chúc bạn học tốt

= 4 x 25 x5

= 100 x 5

=500

4 x 5 x 25

=20 x 25

=500

25/27>23/27

23/27>23/29

=>25/27>23/29