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\(\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}:\dfrac{22}{28}\)
\(=\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}\times\dfrac{14}{11}\)
\(=\dfrac{11\times12\times13\times14}{12\times13\times14\times11}\)
\(=1\)
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\(3\times\dfrac{7}{10}+\dfrac{7}{10}\times5+2\times\dfrac{7}{10}\)
\(=\dfrac{7}{10}\times\left(3+5+2\right)\)
\(=\dfrac{7}{10}\times10=7\)
\(\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}:\dfrac{22}{28}\)
\(=\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}:\dfrac{11}{14}\)
\(=\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}\times\dfrac{14}{11}\)
\(=\dfrac{11\times12\times13\times14}{12\times13\times11\times14}\)
\(=1\)
\(3\times\dfrac{7}{10}+\dfrac{7}{10}\times5+2\times\dfrac{7}{10}\)
\(=\dfrac{7}{10}\times\left(3+5+2\right)\)
\(=\dfrac{7}{10}\times10\)
\(=7\)
câu a) lấy mẫu số chung cộng với nhau
câu b) lấy 1 để ngoài nhân r 1/2-1/3 rồi tương tự
\(\dfrac{12}{13}+\dfrac{2}{7}+\dfrac{8}{13}+\dfrac{6}{13}+\dfrac{5}{7}\)
\(=\left(\dfrac{12}{13}+\dfrac{8}{13}+\dfrac{6}{13}\right)+\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\)
\(=2+1\)
\(=3\)
= ( 12/13 + 8/13 + 6/13 ) + ( 2/7 + 5/7 )
= 26/13 + 7/7
= 2 + 1
= 3
\(\frac{17}{12}+\frac{3}{5}+\frac{19}{12}+\frac{8}{13}+\frac{2}{5}+\frac{18}{13}\)
\(=\left(\frac{17}{12}+\frac{19}{12}\right)+\left(\frac{8}{13}+\frac{18}{13}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=3+2+1\)
\(=6\)
\(\frac{3}{7}\) \(< \) \(\frac{2}{3}\)
\(\frac{6}{7}\)\(=\) \(\frac{12}{14}\)
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+34+25+26+27+28+29+30=475
12/13 + 2/7 + 8/13 + 6/13 + 5/7
= ( 2/7 + 5/7 ) + ( 12/13 + 8/13 + 6/13 )
= 1 + 2
= 3
`(12/26+5/8)+7/13`
`=(6/13+5/8)+7/13`
`=(6/13+7/13)+5/8`
`=1+5/8=13/8`
`(12/26 +5/8) +7/13 `
`= 6/13 + 5/8 + 7/13`
`= (6/13 + 7/13) + 5/8`
`= 13/13 + 5/8`
`= 1 + 5/8 `
`= 8/8 + 5/8 `
`= 13/8`
Ta có :
\(\frac{3}{5}+\frac{7}{12}+\frac{13}{12}=\frac{3}{5}+\frac{7+13}{12}=\frac{3}{5}+\frac{20}{12}\)
\(=\frac{3}{5}+\frac{10}{6}=\frac{18}{30}+\frac{50}{30}=\frac{18+50}{30}=\frac{68}{30}=\frac{34}{15}\)
Đáp số : 34/15
3/5+7/12+13/12=34/15