7/15:11/45
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
( 7/20 + 11/15 - 15/12 ) : ( 11/20 - 26/45 )
= -1/6 : -1/36
= -5/36
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{7}{20}+\frac{11}{15}-\frac{15}{12}\right):\left(\frac{11}{20}-\frac{26}{45}\right)\)
\(=\left(\frac{21}{60}+\frac{44}{60}-\frac{75}{60}\right):\left(\frac{99}{180}-\frac{104}{180}\right)\)
\(=-\frac{1}{6}:\frac{-1}{36}\)
\(=\frac{-36}{-6}\)
\(=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
1.
\(\left(572\cdot7+266\right)\cdot\left(366\cdot9-168\cdot18\right)\cdot\left(346\cdot6-348\right)\)
\(=\left(286\cdot7\cdot2+133\cdot2\right)\cdot\left(366\cdot9-168\cdot2\cdot9\right)\cdot\left(173\cdot6\cdot2-174\cdot2\right)\)
\(=\left(2002\cdot2+133\cdot2\right)\cdot\left(366\cdot9-336\cdot9\right)\cdot\left(1038\cdot2-174\cdot2\right)\)
\(=\left[2\cdot\left(2002+133\right)\right]\cdot\left[9\cdot\left(366-336\right)\right]\cdot\left[2\cdot\left(1038-174\right)\right]\)
\(=2\cdot2135\cdot9\cdot30\cdot2\cdot864\)
\(=4270\cdot9\cdot30\cdot2\cdot864\)
\(=\left(4270\cdot30\right)\cdot9\cdot2\cdot864\)
\(=\left(427\cdot10\right)\cdot\left(3\cdot10\right)\cdot9\cdot2\cdot864\)
\(=\left(427\cdot3\right)\cdot\left(10\cdot10\right)\cdot9\cdot2\cdot864\)
\(=1281\cdot100\cdot9\cdot2\cdot864\)
\(=\left(1281\cdot100\right)\cdot\left(9\cdot2\cdot864\right)\)
\(=\left(1281\cdot100\right)\cdot15552\)
\(=\left(1281\cdot15552\right)\cdot100\)
\(=19922112\cdot100\)
\(=1992211200\)
2.
\(\left(1+3+5+7+...+97+9\right)\cdot\left(45\cdot3-15\cdot2-45\right)\)
\(=\left(1+3+5+7+...+97+9\right)\cdot\left(15\cdot3\cdot3-15\cdot2-15\cdot3\right)\)
\(=\left(1+3+5+7+...+97+9\right)\cdot\left[15\cdot\left(3\cdot3\right)-15\cdot2-15\cdot3\right]\)
\(=\left(1+3+5+7+...+97+9\right)\cdot\left(15\cdot9-15\cdot2-15\cdot3\right)\)
\(=\left(1+3+5+7+...+97+9\right)\cdot\left[15\cdot\left(9-2-3\right)\right]\)
\(=\left(1+3+5+7+...+97+9\right)\cdot15\cdot4\)
\(=\left[\left(1+3+5+7+...+97\right)+9\right]\cdot\left(15\cdot4\right)\)
Trong \(\left(1+3+5+7+...+97\right)\) có số số hạng là:
\(\left(97-1\right)\div2+1=49\) ( số hạng )
\(\Rightarrow\left[\left(1+3+5+7+...+97\right)+9\right]\cdot\left(15\cdot4\right)\)
\(=\left[\left(97+1\right)\cdot49\div2\right]\cdot\left(15\cdot4\right)\)
\(=2401\cdot60\)
\(=\left(2401\cdot6\right)\cdot10\)
\(=14406\cdot10\)
\(=144060\)
3.
\(\left(180\div15-132\div11\right)\cdot\left(57869-297\div11\cdot108\right)\)
\(=\left(12-12\right)\cdot\left(57869-297\div11\cdot108\right)\)
\(=0\cdot\left(57869-297\div11\cdot108\right)\)
\(=0\)
Sửa lại bài 2; dòng 11 ( từ đề bài bài 2 ):
\(=\left\{\left[\left(97+1\right)\cdot49\div2\right]+9\right\}\cdot\left(15\cdot4\right)\)
\(=\left(2401+9\right)\cdot\left(15\cdot4\right)\)
\(=2410\cdot\left(15\cdot4\right)\)
\(=2410\cdot60\)
\(=\left(241\cdot10\right)\cdot\left(6\cdot10\right)\)
\(=\left(241\cdot6\right)\cdot\left(10\cdot10\right)\)
\(=1446\cdot10\)
\(=14460\)
![](https://rs.olm.vn/images/avt/0.png?1311)
`4/7+4`
`=4/7+4/1`
`=4/7+28/7`
`=32/7`
__
`3+6/11`
`=33/11+6/11`
`=39/11`
__
`3-5/7`
`=3/1-5/7`
`=21/7-5/7`
`=16/7`
__
`21/9-2`
`=21/9-18/9`
`=3/9`
`=1/3`
__
`15/24+2`
`=15/24+48/24`
`=63/24`
`=21/16`
__
`63/45-20/25`
`=63/45-4/5`
`=63/45-36/45`
`=27/45`
`=9/15`
__
`3/4-2/8`
`=3/4-1/4`
`=2/4`
__
`6/7-5/8`
`=48/56-35/56`
`=13/56`
__
`37/45-5/9`
`=37/45-25/45`
`=12/45`
`=4/15`
__
`46/39-11/13`
`=46/39-33/39`
`=13/39`
`=1/2`
__
`5/12+3/4+1/3`
`=5/12+9/12+4/12`
`=14/12+4/12`
`=18/12`
`=3/2`
__
`1/2+3/7+11/14`
`=7/14+6/14+11/14`
`=13/14+11/14`
`=24/14`
`=12/7`
__
`7/10-(1/5+1/4)`
`=7/10-(4/20+5/20)`
`=7/10-9/20`
`=14/20-9/20`
`=5/20`
`=1/4`
__
`15/4-2/3-3/4`
`=(15/4-3/4)-2/3`
`=12/4-2/3`
`=3-2/3`
`=9/3-2/3`
`=7/3`
![](https://rs.olm.vn/images/avt/0.png?1311)
dễ mà bạn, dựa vào kiến thức dẫ học kết hợp với việc bạn làm nháp và dùng máy tính để hỗ trợ thì chắc chắc những bài trên chỉ là chuyện nhỏ
![](https://rs.olm.vn/images/avt/0.png?1311)
4 : 9 = \(\dfrac{4}{9}\) 8 : 11 =\(\dfrac{8}{11}\) 7 : 15 =\(\dfrac{7}{15}\)
15 : 5 = \(\dfrac{15}{5}=\dfrac{3}{1}\) 63 : 21 =\(\dfrac{63}{21}\) 45 : 9 =\(\dfrac{45}{9}=\dfrac{5}{1}\)
6 : 18 = \(\dfrac{6}{18}=\dfrac{1}{3}\) 144 : 24 =\(\dfrac{244}{24}\) 7 =\(\dfrac{7}{1}\)
15 = \(\dfrac{15}{1}\) 10 = \(\dfrac{10}{1}\) 0 =\(\dfrac{0}{1}\)
\(4:9=\dfrac{4}{9};15:5=\dfrac{15}{5}=3;6:18=\dfrac{6}{18}=\dfrac{1}{3}\\ 15=\dfrac{15}{1};8:11=\dfrac{8}{11};63:21=\dfrac{63}{21}=3;144:24=\dfrac{144}{24};10=\dfrac{10}{1}\\ 7:15=\dfrac{7}{15};45:9=\dfrac{45}{9}=5;7=\dfrac{7}{1};0=0\)
![](https://rs.olm.vn/images/avt/0.png?1311)
???????????????????????????????????????????????????????????????????????
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\left(\dfrac{5}{12}.\dfrac{21}{15}\right):\dfrac{1}{4}\)
\(=\dfrac{7}{12}:\dfrac{1}{4}\)
\(=\dfrac{28}{12}=\dfrac{7}{3}\)
\(B=\left(\dfrac{2}{7}:\dfrac{5}{4}\right).\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\dfrac{5}{16}\)
\(=\dfrac{1}{14}\)
\(C=\left(\dfrac{11}{15}.\dfrac{35}{44}\right).\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\dfrac{4}{91}\)
\(=\dfrac{1}{39}\)
\(D=\left(\dfrac{7}{20}+\dfrac{11}{15}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\left(\dfrac{13}{12}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\dfrac{-1}{36}\)
\(=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
21.35-3.25.7
= 21.35-21.25
= 21.(35-25)
= 21. 10
=210
77 - 11.( 30+7)
= 11.7 -11.30 -11.7
= 11.7-11.7 -11.30
= -11.30
= -330
21.35-3.25.7=210
77-11(30+7)=-330
85(35-27)-35(85-27)=-1350
47(45-15)-47(45+15)=-2820
=21/11 nha