36/20+15/20= 51/20

7/9-6/9= 1/9

\(\dfrac{9}{5}+\dfrac{3}{4}=\dfrac{36}{20}+\dfrac{15}{20}=\dfrac{36+15}{20}=\dfrac{51}{20}\)

\(\dfrac{7}{9}-\dfrac{2}{3}=\dfrac{7}{9}-\dfrac{6}{9}=\dfrac{1}{9}\)

a) 2/5 + 1/2 + 7/10

= 4/10 + 5/10 + 7/10

= 9/10 + 7/10

= 16/10 = 8/5

b) 4/9 + 11/8 - 5/6

= 32/72 + 99/72 - 60/72

= 191/72

c) 9/20 - 8/15 x 5/12

= 9/20 - 2/9

= 41/180

d) 2/3 : 4/5 : 7/12

= 5/6 : 7/12

= 10/7

a,2/5+1/2+7/10

=4/10+5/10+7/10

=16/10

=8/5

b,4/9+11/8-5/6

=32/72+99/72-5/6

=131/72-5/6

=131/72-60/72

=71/72

c,9/20-8/15x5/12

=9/20-2/9

=41/180

d,2/3:4/5:7/12

=2/5x5/4x12/7

=6/7

`3/7xx14/5+32/5xx3/7+3/7xx9/5`

`=3/7xx(14/5+32/5+9/5)`

`=3/7xx55/5`

`=3/7xx5`

`=15/7`

\(=\frac{3}{7}\times[\frac{14}{5}+\frac{32}{5}+\frac{9}{5}]=\frac{3}{7}\times\frac{55}{5}=\frac{3}{7}\times11=\frac{33}{7}\)

Có số các số hạng là:       (79 - 3)/4 +1 = 20 (số hạng)

\(\frac{44\cdot66+34\cdot41}{3+7+11+...+79}=\frac{11\cdot2^2\cdot11\cdot2\cdot3+17\cdot2\cdot41}{3+7+11+...+79}=\frac{2\cdot3\cdot\left(11^2\cdot2+17\cdot41\right)}{\left(3+79\right)\cdot20:2}=\frac{5634}{820}=\frac{2817}{410}\)

<                     <                            =

>                     >                          >

<                  >                        =

Mình nhanh nhất

5/7 < 4/3                    2/5 < 6/10                   1/4 = 3/12

27/36 > 2/9                 7/6 > 7/9                     7/2 > 4/79

15/23 < 1                    27/9 > 2                      51/17 = 3/1

Mình làm vậy đúng hơm nà??? ==

5/7<4/3                 2/5<6/10            1/4=3/12

27/36<2/9             7/6>7/9              7/2>4/79

15/23<1                29/9>2               51/17=3/1

`( 9 xx 6 xx 5 xx 7 )/( 19 xx 7 xx 2 xx 3 )`

`= ( 9 xx 2 xx 3 xx 7 xx 5 )/( 19 xx 7 xx 2 xx 3 )`

`= (9xx5)/19` 

`= 45/19` 

= 9 x 6 x 5 x 7/19 x 7 x 2 x3