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\(\dfrac{2}{5}\times\dfrac{3}{4}-\dfrac{1}{8}=\dfrac{1}{5}\times\dfrac{3}{2}-\dfrac{1}{8}=\dfrac{3}{10}-\dfrac{1}{8}=\dfrac{24}{80}-\dfrac{10}{80}=\dfrac{14}{80}=\dfrac{7}{40}\\ \dfrac{4}{3}+\dfrac{1}{3}-\dfrac{1}{5}=\dfrac{5}{3}-\dfrac{1}{5}=\dfrac{25}{15}-\dfrac{3}{15}=\dfrac{22}{15}\\ \dfrac{9}{20}-\dfrac{3}{5}\times\dfrac{1}{4}=\dfrac{9}{20}-\dfrac{3}{20}=\dfrac{6}{20}=\dfrac{3}{10}\\ \dfrac{2}{8}+\dfrac{2}{3}:\dfrac{4}{5}=\dfrac{2}{8}+\dfrac{2}{3}\times\dfrac{5}{4}=\dfrac{2}{8}+\dfrac{1}{3}\times\dfrac{5}{2}=\dfrac{2}{8}+\dfrac{5}{6}=\dfrac{1}{4}+\dfrac{5}{6}=\dfrac{6}{24}+\dfrac{20}{24}=\dfrac{26}{24}=\dfrac{13}{12}\)
a) \(\dfrac{2}{7}\times\dfrac{4}{3}+\dfrac{2}{6}\)
\(=\dfrac{8}{21}+\dfrac{2}{6}\)
\(=\dfrac{5}{7}\)
b) \(\dfrac{4}{7}:2+\dfrac{4}{7}\)
\(=\dfrac{2}{7}+\dfrac{4}{7}\)
\(=\dfrac{6}{7}\)
c) \(\dfrac{1}{3}+\dfrac{3}{4}-\dfrac{1}{5}:\dfrac{2}{3}\)
\(=\dfrac{13}{12}-\dfrac{3}{10}\)
\(=\dfrac{47}{60}\)
a \(\dfrac{8}{21}+\dfrac{2}{6}=\dfrac{16}{42}+\dfrac{14}{42}=\dfrac{30}{42}=\dfrac{5}{7}\)
\(b\) \(\dfrac{4}{7}\times\dfrac{1}{2}+\dfrac{4}{7}=\dfrac{2}{7}+\dfrac{4}{7}=\dfrac{6}{7}\)
\(c\) \(\dfrac{1}{3}+\dfrac{3}{4}-\dfrac{1}{5}\times\dfrac{3}{2}=\dfrac{1}{3}+\dfrac{3}{4}-\dfrac{3}{10}=\dfrac{20}{60}+\dfrac{45}{60}-\dfrac{18}{60}=\dfrac{47}{60}\)
a)
`2/3+5/2-3/4`
`=10/4-3/4+2/3`
`=7/4+2/3`
`=21/12+8/12`
`=29/12`
b)
`2/5xx1/2:1/3`
`=2/10xx3/1`
`=6/10=3/5`
c)
`2/9:2/9xx1/3`
`=2/9xx9/2xx1/3`
`=1xx1/3`
`=1/3`
a, \(\dfrac{2}{3}\) + \(\dfrac{5}{2}\) - \(\dfrac{3}{4}\)
= \(\dfrac{8}{12}\) + \(\dfrac{30}{12}\) - \(\dfrac{9}{12}\)
= \(\dfrac{38-9}{12}\)
= \(\dfrac{29}{12}\)
b, \(\dfrac{2}{5}\) x \(\dfrac{1}{2}\) : \(\dfrac{1}{3}\)
= \(\dfrac{1}{5}\) x \(\dfrac{3}{1}\)
= \(\dfrac{3}{5}\)
c, \(\dfrac{2}{9}\) : \(\dfrac{2}{9}\) x \(\dfrac{1}{3}\)
= 1 x \(\dfrac{1}{3}\)
= \(\dfrac{1}{3}\)
bài 1 :
\(a,\dfrac{2}{7}+\dfrac{1}{3}=\dfrac{6}{21}+\dfrac{7}{21}=\dfrac{13}{21}\)
\(b,\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{9}{15}-\dfrac{5}{15}=\dfrac{4}{15}\)
\(c,\dfrac{13}{4}:5=\dfrac{13}{4}:\dfrac{5}{1}=\dfrac{13}{4}x\dfrac{1}{5}=\dfrac{13}{20}\)
\(d,\dfrac{6}{23}x\dfrac{1}{18}=\dfrac{1}{69}\)
bài 2 :
\(a,x+\dfrac{1}{3}=\dfrac{5}{12}\)
\(x=\dfrac{5}{12}-\dfrac{1}{3}\)
\(x=\dfrac{1}{12}\)
\(b,x:\dfrac{7}{4}=\dfrac{2}{5}\)
\(x=\dfrac{2}{5}x\dfrac{7}{4}\)
\(x=\dfrac{7}{10}\)
bài 3 :
đổi : 2 dm 1cm = 21cm
chiều cao hình bình hành là;
21 x\(\dfrac{3}{7}=\)9(cm)
diện tích hình bình hành là;
21 x 9 =189 (cm2)
đáp số : 189 cm2
bài 4 :
\(\dfrac{2}{3}x\dfrac{2}{10}+\dfrac{2}{3}x\dfrac{5}{10}x\dfrac{3}{3}\)
\(\dfrac{2}{3}x\left(\dfrac{2}{10}+\dfrac{5}{10}\right)x\dfrac{2}{3}\)
=\(\dfrac{2}{3}x1x\dfrac{2}{3}\)
\(=\dfrac{2}{3}x\dfrac{2}{3}\)
=\(\dfrac{4}{9}\)
Bài 1)
a) \(\dfrac{6}{21}+\dfrac{7}{21}=\dfrac{13}{21}\)
b) \(\dfrac{9}{15}-\dfrac{5}{15}=\dfrac{4}{15}\)
c) \(\dfrac{13}{4}x\dfrac{1}{5}=\dfrac{13}{20}\)
d) \(\dfrac{6}{414}=\dfrac{1}{69}\)
Bài 2)
a) \(x=\dfrac{5}{12}-\dfrac{1}{3}\)
\(x=\dfrac{1}{12}\)
b) \(x=\dfrac{2}{5}x\dfrac{7}{4}\)
\(x=\dfrac{7}{10}\)
Bài 3)
2dm 1cm = 21 cm
Chiều cao tấm bìa la
\(21x\dfrac{3}{7}=9\left(cm\right)\)
Diện tích tấm bìa là
\(21x9=189\left(cm2\right)\)
a) \(\dfrac{11}{10}+\dfrac{3}{5}:\dfrac{2}{3}=\dfrac{11}{10}+\dfrac{3}{5}\times\dfrac{3}{2}=\dfrac{11}{10}+\dfrac{9}{10}=\dfrac{20}{10}=2\)
b) \(\dfrac{4}{3}+5\times\dfrac{5}{8}=\dfrac{4}{3}+\dfrac{25}{8}=\dfrac{32}{24}+\dfrac{75}{24}=\dfrac{107}{24}\)
c) \(\left(\dfrac{2}{5}+\dfrac{3}{7}\right)\times\dfrac{25}{29}=\left(\dfrac{14}{35}+\dfrac{15}{35}\right)\times\dfrac{25}{39}=\dfrac{29}{35}\times\dfrac{25}{39}=\dfrac{145}{274}\)
d) \(\dfrac{1}{4}\times\dfrac{5}{12}+\dfrac{5}{12}\times\dfrac{4}{5}=\dfrac{5}{12}\times\left(\dfrac{1}{4}+\dfrac{4}{5}\right)=\dfrac{5}{12}\times\dfrac{21}{20}=\dfrac{105}{240}=\dfrac{7}{16}\)
a) \(\dfrac{11}{10}+\dfrac{3}{5}x\dfrac{3}{2}=\dfrac{11}{10}+\dfrac{9}{10}=\dfrac{20}{10}=2\)
b) \(\dfrac{4}{3}+\dfrac{25}{8}=\dfrac{32}{24}+\dfrac{75}{24}=\dfrac{107}{24}\)
c) \(\dfrac{29}{35}x\dfrac{25}{29}=\dfrac{5}{7}\)
\(=\dfrac{5}{12}x\left(\dfrac{1}{4}+\dfrac{4}{5}\right)=\dfrac{5}{12}x\dfrac{21}{20}=\dfrac{7}{16}\)
:") tìm `x` ?
a) = 5/6 + 1/4 = 13/12
b) = 5/2 + 1/12 = 31/12
c) = 5/2 - 4/3 = 7/6