a] 4/12 ; 5/12 ; 11/2 ; 1/4

b] 1 ; 9/12; 12/5 ; 11/3

c] 8/21; 6/11;8/7

d] 2/3 ;2/7 15/2

a]1/3  5/12     11/2       1/4

b]1      3/4         12/5         33/9

c]8/21      6/11        8/7

d]2/3        2/7          15/2

a) 1/3 ; 5/12 ; 11/2 ; 1/14

b) 1 ; 9/12 ; 12/5 ; 11/3

c) 8/21 ; 6/11 ; 8/7

d) 2/3 ; 2/7 ; 15/2

`4/7 + 3/4 + 2/7 = (4/7 + 2/7 ) +3/4 = 6/7 + 3/4 = 24/28 + 21/28 =45/28`     

`18/7 - 2= 18/7 - 2/1 = 18/7 - 4/7 `             

`10/12 - 12/36=30/36 - 12/36=18/36=1/2`

`5/3 - 3/5 + 6/11=(25/15-9/15) + 6/11 =16/15 + 6/11 = (506+90)/165=596/165`                     

`3/5 xx 3/7 : 5 = 3/5 xx3/7 xx 1/5 = 9/35 xx 1/5 = 9/175`

   \(\dfrac{2}{5}+\dfrac{2}{3}+\dfrac{2}{4}\)

= \(\dfrac{24}{60}\) + \(\dfrac{40}{60}\) + \(\dfrac{30}{60}\)

= \(\dfrac{64}{60}\) + \(\dfrac{30}{60}\)

= \(\dfrac{47}{30}\)

\(\dfrac{2}{6}+\dfrac{3}{12}\)

= \(\dfrac{4}{12}\) + \(\dfrac{3}{12}\)

= \(\dfrac{7}{12}\)

\(\dfrac{5}{6}\) + \(\dfrac{1}{3}\)

= \(\dfrac{5}{6}\) + \(\dfrac{2}{6}\)

= \(\dfrac{7}{6}\)

   \(\dfrac{1}{3}\) + \(\dfrac{5}{12}\) + \(\dfrac{5}{6}\)

= \(\dfrac{4}{12}\) + \(\dfrac{5}{12}\) + \(\dfrac{10}{12}\)

= \(\dfrac{9}{12}\) + \(\dfrac{10}{12}\)

= \(\dfrac{19}{12}\)

    \(\dfrac{5}{8}\) + \(\dfrac{4}{7}\)

= \(\dfrac{35}{56}\) + \(\dfrac{32}{56}\)

=  \(\dfrac{67}{56}\) 

\(\dfrac{7}{3}\) + \(\dfrac{8}{7}\)

= \(\dfrac{49}{21}\) + \(\dfrac{24}{21}\)

= \(\dfrac{73}{21}\)

   \(\dfrac{1}{5}+\dfrac{5}{35}\)

= \(\dfrac{7}{35}\) + \(\dfrac{5}{35}\)

= \(\dfrac{12}{35}\) 

giúp mình

giup minh

\(\dfrac{5}{2}\times\dfrac{3}{7}-\dfrac{3}{4}\div\dfrac{7}{3}=\dfrac{5}{2}\times\dfrac{3}{7}-\dfrac{3}{4}\times\dfrac{3}{7}=\dfrac{5}{2}\times\dfrac{3}{7}-\dfrac{3}{7}\times\dfrac{3}{4}\) 

                           \(=\dfrac{3}{7}\times\left(\dfrac{5}{2}-\dfrac{3}{4}\right)=\dfrac{3}{7}\times\dfrac{7}{4}=\dfrac{3}{4}\) 

\(\dfrac{5}{4}\div\dfrac{15}{12}-\dfrac{5}{4}\div\dfrac{1}{2}=\dfrac{5}{4}\times\dfrac{12}{15}-\dfrac{5}{4}\times2\)

                              \(=\dfrac{5}{4}\times\left(\dfrac{12}{15}-2\right)\) 

                              \(=\dfrac{5}{4}\times\dfrac{-6}{5}=\dfrac{-3}{2}\) 

\(\dfrac{1}{26}+\dfrac{7}{30}+\dfrac{12}{26}+\dfrac{8}{3}=\left(\dfrac{1}{26}+\dfrac{12}{26}\right)+\left(\dfrac{7}{30}+\dfrac{8}{3}\right)\)

                                 \(=\dfrac{1}{2}+\dfrac{29}{10}=\dfrac{17}{5}\)

c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)

\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)

\(=1-2=-1\)

Giải:

a)-1/12+4/3=-1/12+16/12=15/12=5/4

b)(-4/14-3/15)-(1/5-20/35-(-1)).7

=-17/35-22/35.7

=-17/35-22/5

=-171/35

c)3/5+-5/20+30/75+-7/4

=3/5+-1/4+2/5+-7/4

=(3/5+2/5)+(-1/4+-7/4)

=1+-2

=-1

d)5/6.-12/14+7/13

=-5/7+7/13

=-16/91

e)2/-9-5/-36-1/4

=-1/12-1/4

=-1/3

f)2/23+-5/12+7/18+21/23+-7/12

=(2/23+21/23)+(-5/12+-7/12)+7/18

=1+-1+7/18

=7/18

xcsxccsz

Phương pháp giải:

Nhẩm lại bảng nhân, chia đã học rồi điền kết quả vào chỗ trống.

Lời giải chi tiết:

2 × 3 = 6          4 × 8 = 32

12 : 2 = 6         27 : 3 = 9

4 × 7 = 28        5 × 6 = 30

36 : 4 = 9         18 : 2 = 9

3 × 1 = 3          4 × 3 = 12

0 : 5 = 0           3 × 4 = 12

1 × 8 = 8          12 : 4 = 3

0 : 3 = 0           12 : 3 = 4

tính bằng cách thuận tiện nhất

a x 3,7 + a x 5,3 + a = 45

    \(\dfrac{7}{6}\) + \(\dfrac{5}{12}\) - \(\dfrac{1}{18}\) - 1 

=  \(\dfrac{42}{36}\) + \(\dfrac{15}{36}\) - \(\dfrac{2}{36}\) - \(\dfrac{36}{36}\)

= \(\dfrac{19}{36}\)

\(\dfrac{13}{6}\) + \(\dfrac{5}{18}+3-\dfrac{7}{12}\)

= \(\dfrac{78}{36}+\dfrac{10}{36}+\dfrac{108}{36}-\dfrac{21}{36}\)

= \(\dfrac{175}{36}\)

3 + \(\dfrac{11}{4}-\dfrac{1}{12}-\dfrac{3}{16}\)

= \(\dfrac{144}{48}+\dfrac{132}{48}-\dfrac{4}{48}-\dfrac{9}{48}\)

= \(\dfrac{263}{48}\)

   \(\dfrac{2}{5}\) x \(\dfrac{7}{4}\) - \(\dfrac{2}{5}\) x \(\dfrac{3}{4}\)

=  \(\dfrac{2}{5}\) x ( \(\dfrac{7}{4}\) - \(\dfrac{3}{4}\))

= \(\dfrac{2}{5}\)  x \(\dfrac{4}{4}\)

= \(\dfrac{2}{5}\)

Ko bết

khó quá mk giải miết mà không ra

khó vãi