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=17/21 x 3/5 + 17/ 21 x 2/5
= 17/ 21 x ( 3/5 + 2/5 )
= 17/ 21x 1
= 17/21
Hok tốt !!!
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![](https://rs.olm.vn/images/avt/0.png?1311)
CÁCH 1:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{35}+\frac{34}{105}=\frac{17}{21}\)
CÁCH 2:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{21}\times(\frac{3}{5}+\frac{2}{5})=\frac{17}{21}\times1=\frac{17}{21}\)
Cách 1:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)
\(=\frac{3\times17}{5\times21}+\frac{17\times2}{21\times5}\)
\(=\frac{17}{5\times7}+\frac{34}{105}\)
\(=\frac{17}{35}+\frac{34}{105}\)
\(=\frac{17\times3}{35\times3}+\frac{34}{105}\)
\(=\frac{51+34}{105}\)
\(=\frac{85}{105}\)
\(=\frac{17}{21}\)
Cách 2:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)
\(=\frac{17}{21}\times\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=\frac{17}{21}\times1\)
\(=\frac{17}{21}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
C1 : 3/5 + 17/21 + 17/21 x 2/5
= 3/5 + 17/21 x ( 1 + 2/5 )
= 3/5 + 17/21 x ( 5/5 + 2/5 )
= 3/5 + 17/21 x 7/5
= 3/5 + 17/15
= 9/15 + 17/15
= 26/15
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a: \(=\dfrac{3}{22}\cdot22\cdot\dfrac{3}{11}=3\cdot\dfrac{3}{11}=\dfrac{9}{11}\)
b: \(=\dfrac{5}{6}\cdot\dfrac{2}{5}=\dfrac{1}{3}\)
c: =17/21(3/5+2/5)=17/21
![](https://rs.olm.vn/images/avt/0.png?1311)
`a)3/5xx17/21+17/21xx2/5`
`=17/21xx(3/5+2/5)`
`=17/21xx1=17/21`
`b)(8/5+5/6):7/6`
`=(48/30+25/30)xx6/7`
`=73/30xx6/7`
`=73/35`
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(=\dfrac{3}{22}\cdot22\cdot\dfrac{3}{11}=3\cdot\dfrac{3}{11}=\dfrac{9}{11}\)
b: \(=\dfrac{5}{6}\cdot\dfrac{2}{5}=\dfrac{1}{3}\)
c: \(=\dfrac{17}{21}\left(\dfrac{3}{5}+\dfrac{2}{5}\right)=\dfrac{17}{21}\)
\(\frac{17}{21}\times\frac{2}{5}+\frac{17}{21}\times\frac{17}{21}\times\frac{3}{5}\)
\(=\frac{17}{21}\times\left(\frac{2}{5}+\frac{3}{5}\right)\)
\(=\frac{17}{21}\times1\)
\(=\frac{17}{21}\)
Đề bài hơi kì. Bạn kiểm tra lại xem có sai chỗ nào ko v?