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\(\dfrac{7}{5}+\dfrac{4}{7}-\dfrac{9}{10}=\dfrac{49-20}{35}-\dfrac{9}{10}=\dfrac{19}{35}-\dfrac{9}{10}=\dfrac{190-315}{350}=\dfrac{-125}{350}\)
\(\dfrac{2}{1}+\dfrac{3}{4}\text{×}\dfrac{8}{5}=\dfrac{8+3}{4}\text{×}\dfrac{8}{5}=\dfrac{11\text{×}8}{4\text{×}5}=\dfrac{88}{20}\)
mấy câu kia áp dụng là dc!
\(\frac{4}{3}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}:\frac{9}{8}\)
=\(\frac{4}{3}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
=\(\frac{16}{27}\)
1. a
\(\dfrac{8}{5}-\dfrac{5}{6}\cdot\dfrac{3}{4}\)
\(=\dfrac{8}{5}-\dfrac{5\cdot3}{3\cdot2\cdot4}\)
\(=\dfrac{8}{5}-\dfrac{5}{8}=\dfrac{39}{40}\)
1.b
\(=\dfrac{7}{8}+\dfrac{5}{6}\cdot\dfrac{3}{2}\)
\(=\dfrac{7}{8}+\dfrac{5\cdot3}{3\cdot2\cdot2}\)
\(=\dfrac{7}{8}+\dfrac{5}{4}=\dfrac{17}{8}\)
2.a
\(\dfrac{4}{5}+x=\dfrac{11}{10}\)
\(x=\dfrac{11}{10}-\dfrac{4}{5}=\dfrac{3}{10}\)
2.b
\(x-\dfrac{3}{4}=\dfrac{5}{7}\)
\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)
=43/12-16/6.(20/32+7/32)
=43/12-16/6.27/32
=43/12-9/4
=43/12-27/12
=4/3
43/12-16/6x[5/8+7/32]
=43/12-16/6x[20/32+7/32]
=43/12-16/6x27/32
=43/12-432/192
=688/192-432-192
=256/192=4/3
1.
=3/5x(3/7+4/7)+2/5x(13/9-4/9)
=3/5x1+2/5x1
=3/5+2/5
=1
2.Xx(3/4+4/5)=7/10
Xx31/20=7/10
X =7/10:31/20
X =14/31
\(\frac{3}{5}\cdot\frac{3}{7}+\frac{3}{5}\cdot\frac{4}{7}+\frac{2}{5}\cdot\frac{13}{9}-\frac{2}{5}\cdot\frac{4}{9}\)
\(=\frac{3}{5}\cdot\left(\frac{3}{7}+\frac{4}{7}\right)+\frac{2}{5}\cdot\left(\frac{13}{9}-\frac{4}{9}\right)\)
\(=\frac{3}{5}\cdot1+\frac{2}{5}\cdot1\)\(=\frac{3}{5}+\frac{2}{5}=1\)
_________________________________________
\(\frac{3}{4}\cdot x+\frac{4}{5}\cdot x=\frac{7}{10}\)
\(\left(\frac{3}{4}+\frac{4}{5}\right)\cdot x=\frac{7}{10}\)
\(\frac{31}{20}\cdot x=\frac{7}{10}\)
\(x=\frac{7}{10}:\frac{31}{20}\)
\(x=\frac{14}{31}\)
\(\frac{5}{6}+\frac{7}{9}:\frac{5}{6}-\frac{1}{6}\)
\(=\left(\frac{5}{6}-\frac{1}{6}\right)+\frac{7}{9}.\frac{6}{5}\)
\(=\frac{2}{3}+\frac{14}{15}\)
\(=\frac{10}{15}+\frac{14}{15}=\frac{24}{15}\)
\(\frac{8}{11}.\frac{7}{8}+\frac{8}{11}:\frac{4}{5}\)
\(=\frac{7}{11}+\frac{8}{11}.\frac{5}{4}\)
\(=\frac{7}{11}+\frac{10}{11}\)
\(=\frac{17}{11}\)
\(\frac{5}{6}+\frac{7}{9}:\frac{5}{6}-\frac{1}{6}\) \(\frac{8}{11}x\frac{7}{8}+\frac{8}{11}:\frac{4}{5}\)
\(=\frac{5}{6}+\frac{14}{15}-\frac{1}{6}\) \(=\frac{8}{11}x\frac{7}{8}+\frac{8}{11}x\frac{5}{4}\)
\(=\left(\frac{5}{6}-\frac{1}{6}\right)+\frac{14}{15}\) \(=\frac{8}{11}x\left(\frac{7}{8}+\frac{5}{4}\right)\)
\(=\frac{2}{3}+\frac{14}{15}\) \(=\frac{8}{11}x\frac{17}{8}\)
\(=\frac{8}{5}\) \(=\frac{17}{11}\)
Tính :
\(\frac{2}{5}\)x \(\frac{3}{4}\)+ \(\frac{8}{15}\): \(\frac{2}{3}\)x 5 = \(\frac{3}{10}\)+ \(\frac{4}{5}\)x 5
= \(\frac{3}{10}\)+ 4
= \(\frac{43}{10}\)
Tính :
7 ngày 15 giờ : 3 = 2 ngày 13 giờ
40/42 dễ
Bài làm :
\(\frac{5}{6}\times\frac{8}{7}\)
\(=\frac{5\times4\times2}{2\times3\times7}\)
\(=\frac{20}{21}\)
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