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a) Các phân số tối giản là: \(\dfrac{4}{5};\dfrac{3}{4};\dfrac{11}{13}\)
b) Các phân số bằng phân số \(\dfrac{5}{7}\) là: \(\dfrac{25}{35};\dfrac{100}{140};\dfrac{85}{119}\)
( \(\dfrac{2}{15}\) - \(\dfrac{1}{20}\) + \(\dfrac{3}{15}\) - \(\dfrac{9}{28}\) + \(\dfrac{2}{3}\)) : \(\dfrac{3}{4}\)
= { (\(\dfrac{2}{15}\) + \(\dfrac{3}{15}\)) + \(\dfrac{2}{3}\) - (\(\dfrac{1}{20}\) + \(\dfrac{9}{28}\))} : \(\dfrac{3}{4}\)
= { \(\dfrac{1}{3}\) + \(\dfrac{2}{3}\) - \(\dfrac{13}{35}\)) : \(\dfrac{3}{4}\)
= ( 1 - \(\dfrac{13}{35}\)): \(\dfrac{3}{4}\)
= \(\dfrac{22}{35}\) : \(\dfrac{3}{4}\)
= \(\dfrac{88}{105}\)
a: =2/5+3/5=1
b: =1/3+2/3=1
c: =7/8+5/8=12/8=3/2
d: =2/7+3/7=5/7
\(a,\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\\ b,\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\\ c,\dfrac{7}{8}+\dfrac{5}{8}=\dfrac{12}{8}=\dfrac{3}{2}\\ d,\dfrac{1}{7}+\dfrac{3}{7}=\dfrac{4}{7}\)
11/9-5/6:15
=11/9-5/6.1/15
=11/9-1/18
=7/6
3/16+(-7/30).15/28
=3/16+(-1/8)
=3/16+(-2/16)
=1/16
\(\dfrac{11}{9}-\dfrac{5}{6}:15=\dfrac{11}{9}-\dfrac{5}{6}\times\dfrac{1}{15}=\dfrac{11}{9}-\dfrac{5}{90}=\dfrac{110}{90}-\dfrac{5}{90}=\dfrac{105}{90}=\dfrac{7}{6}\)
\(\dfrac{3}{16}+\dfrac{-7}{30}\times\dfrac{15}{28}=\dfrac{3}{16}+\left(-\dfrac{1}{8}\right)=\dfrac{3}{16}-\dfrac{1}{8}=\dfrac{3}{16}-\dfrac{2}{16}=\dfrac{1}{16}\)
\(\dfrac{5}{12}\times\dfrac{28}{15}+\dfrac{7}{3}\)
\(=\dfrac{7}{9}+\dfrac{7}{3}\)
\(=\dfrac{7}{9}+\dfrac{21}{9}\)
\(=\dfrac{28}{9}\)
\(\dfrac{5}{12}.\dfrac{28}{15}+\dfrac{7}{3}=\dfrac{7}{9}+\dfrac{7}{3}=\dfrac{7}{9}+\dfrac{21}{9}\)
\(=\dfrac{28}{9}\)
\(\frac{15}{16}:\frac{35}{4}=\frac{3}{28}\) \(\frac{12}{51}:\frac{1}{17}=4\)
chúc bạn học tốt!
\(\dfrac{7}{15}+\dfrac{4}{5}\)
\(=\dfrac{7}{15}+\dfrac{12}{15}\)
\(=\dfrac{19}{15}\)
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\(\dfrac{35}{28}-\dfrac{48}{64}\)
\(=\dfrac{2240}{1792}-\dfrac{1344}{1792}\)
\(=\dfrac{896}{1792}=\dfrac{1}{2}\)
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\(\dfrac{10}{13}:\dfrac{3}{4}\)
\(=\dfrac{10}{13}\)x\(\dfrac{4}{3}\)
\(=\dfrac{40}{39}\)
\(\dfrac{3}{28}+\dfrac{15}{140}=\dfrac{3}{28}+\dfrac{3}{28}=\dfrac{6}{28}=\dfrac{3}{14}\)
= 3/14 nha em