Giải thích hơi dài, tớ chỉ ghi đ/s thôi.

Đ/s: 1.

20/11*33/23*69/180=20*33*69/11*23*180=9/9=1

a)\(\frac{20}{11}.\frac{33}{23}.\frac{69}{180}=\frac{9}{9}=1\)

b: (675,98 + 888,66 + 111,34) x 0,01

= (675,98 + [888,66 + 111,34]) x 0,01

= (675,98 + 1000) x 0,01

= 1675,98 x 0,01

= 16,7598 

(675,98 + 888,66 + 111,34) x 0,01

= (675,98 + [888,66 + 111,34]) x 0,01

= (675,98 + 1000) x 0,01

= 1675,98 x 0,01

= 16,7598 

20/11x33/23x69/180

=(20/11x69/180)x33/23

=23/33 x 33/23

=1

20,11x96+20,11:0,25

=20,11x96+20,11x4

=20,11x100

=201,1

20, 11×96+20, 11:0, 25

= 20,11 x 96 + 20,11 x 4

= 20,11 x ( 96 + 4 )

= 20,11 x 100

= 2011

   20,11 x 96 + 20,11 : 0,25

= 20,11 x 96 + 20,11 x 4

= 20,11 x (96+4)

= 20,11 x 100

= 2011

= 0

( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 6 x 7 ) 

= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 42 )

= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x 0

= 0

=0 nha

\(\dfrac{1}{3}+\dfrac{6}{5}-\dfrac{1}{5}+\dfrac{2}{3}=2\)

1/3+6/5−1/5+2/3=2

\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)

\(=\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)

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

\(=\frac{1}{2}-\frac{1}{6}\)

\(=\frac{1}{3}\)

2,5 x 12 ,5 x 8 x 0,4=(2,5 x 0,4 ) x(12,5 x8)

                            =1x100=100

=2,5 x 12,5 x 8 x 0,4

=(2,5 x 0,4) x (12,5 x 8)

=1 x 100

=100

Tính bằng cách thuận tiện nhất: 2,5x12,5x8x0,4=100

k mik nha

1212/1515 = 1212 :1515 

= 12 x 101 : 15 x 101 

= 12/15

dinh hoang vu

\(\frac{1212}{1515}=\frac{1212\div101}{1515\div101}\)

\(=\frac{12}{15}=\frac{4}{5}\)

\(\frac{1212}{1515}=\frac{2^2.3.101}{3.5.101}=\frac{2^2}{5}=\frac{4}{5}\)