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`3/7+2/5+4/7`
`=(3/7+4/7)+2/5`
`=1+2/5`
`=5/5+2/5`
`=7/5`
`20/34+4/9+7/17`
`=(20/34+7/17)+4/9`
`=(20/34+14/34)+4/9`
`=34/34+4/9`
`=1+4/9`
`=9/9+4/9`
`=13/9`
`48xx2+96+48xx6`
`=48xx2+48xx2+48xx6`
`=48xx(2+2+6)`
`=48xx10`
`=480`
câu thứ hai thì làm như này em nhé:
\(\dfrac{20}{34}\) + \(\dfrac{4}{9}\) + \(\dfrac{7}{17}\)
= (\(\dfrac{20}{34}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)
= (\(\dfrac{10}{17}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)
= 1 + \(\dfrac{4}{9}\)
= \(\dfrac{13}{9}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\left(56\times27+56\times35\right)\div62=56\times\left(27+35\right)\div62=56\times62\div62=56\)
b) \(\frac{0,18\times1230+0,9\times4567\times2+3\times5310\times6}{1+4+7+10+....+52+55-514}\)
\(=\frac{0,18\times1230+\left(0,9\times2\right)\times4567+\left(3\times6\right)\times5310}{1+4+5+.....+52+55-514}\)
\(=\frac{0,18\times1230+0,18\times4567+0,18\times5310}{1+4+7+...+52+55-514}\)
\(=\frac{0,18\times\left(1230+4567+5310\right)}{\left(55+1\right)\times55\div2-514}\)
\(=\frac{0,18\times11107}{971}=\frac{1999,26}{971}\)
mình ra cũng giống bạn Forever _ Alone nhé!!!Chẳng qua mình không biết viết phân số
![](https://rs.olm.vn/images/avt/0.png?1311)
1.
= 10 000 - 29 x 11
= 10 000 - 319
= 9681
2.
= ( 3/7 + 4/7 ) + ( 4/9 + 5/9 )
= 1 + 1
= 2
![](https://rs.olm.vn/images/avt/0.png?1311)
bài 1
\(\frac{2}{5}+x=4\) , \(\frac{8}{7}:x=\frac{4}{5}\)
\(\Rightarrow\)\(x=4-\frac{2}{5}\) , \(\Rightarrow\)\(x=\frac{8}{7}:\frac{4}{5}\)
\(\Rightarrow\)\(x=\frac{18}{5}\) , \(\Rightarrow\) \(x=\frac{10}{7}\)
tính cách thuận tiện là dấu = là x vì viết nhầm
![](https://rs.olm.vn/images/avt/0.png?1311)
4/9 x (3/5-1/5) +4/9 -7/5 x 4/9
= 4/9 x 2/5 + 4/9 x 1 - 4/9 x 7/5
= 4/9 x (2/5+1-7/5)
=4/9 x 0
=0.
tick mk nha
HT
4/9 x (3/5-1/5) +4/9 -7/5 x 4/9
= 4/9 x 2/5 + 4/9 x 1 - 4/9 x 7/5
= 4/9 x (2/5+1-7/5)
=4/9 x 0
=0.
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{21}{16}\times\dfrac{8}{5}\times\dfrac{15}{7}=\dfrac{21\times8\times15}{16\times5\times7}=\dfrac{7\times3\times8\times5\times3}{8\times2\times5\times7}=\dfrac{3\times3}{2}=\dfrac{9}{2}\)
\(\dfrac{18}{9}\times\dfrac{9}{36}\times\dfrac{27}{3}=2\times\dfrac{1}{4}\times9=\dfrac{1}{2}\times9=\dfrac{9}{2}\)
TL :
2 x 9 + 5 x 9 + 27
= 2 x 9 + 5 x 9 + 3 x 9
= 9 x ( 2 + 5 + 3 )
= 9 x 10
= 90
~HT~
bạn biết nhân 2 chữ số với 2 chữ số rồi à