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a. \(\dfrac{x}{5}=\dfrac{8}{10}\)
\(\Rightarrow10x=8.5\)
\(\Rightarrow10x=40\)
\(\Rightarrow x=\dfrac{40}{10}=4\)
b. \(\dfrac{9}{x}=\dfrac{90}{100}\)
\(\Rightarrow9.100=90x\)
\(\Rightarrow900=90x\)
\(\Rightarrow x=\dfrac{900}{90}=10\)
c. \(17+\dfrac{x}{35}=\dfrac{5}{7}\)
\(\Rightarrow\dfrac{595+x}{35}=\dfrac{25}{35}\)
\(\Rightarrow595+x=25\)
\(\Rightarrow x=25-595=-570\)
d. \(x:\dfrac{5}{27}=\dfrac{2}{9}\)
\(\Rightarrow\dfrac{27x:5}{27}=\dfrac{6}{27}\)
\(\Rightarrow27x:5=6\)
\(\Rightarrow27x=5.6\)
\(\Rightarrow27x=30\)
\(\Rightarrow x=\dfrac{30}{27}=\dfrac{10}{9}\approx1,11\)
\(a,x=\dfrac{1}{2}-\dfrac{2}{5}\)
\(x=\dfrac{1}{10}\)
\(b,x+\dfrac{3}{7}=\dfrac{7}{10}\)
\(x=\dfrac{7}{10}-\dfrac{3}{7}\)
\(x=\dfrac{19}{70}\)
\(c,19-x=\dfrac{17}{20}\)
\(x=19-\dfrac{17}{20}\)
\(x=\dfrac{363}{20}\)
a: x=9/2-3/7=57/14
b: =>x=7/5x5/7=1
c: =>x=11/3:3/8=11/3x8/3=88/9
a : x = \(\dfrac{9}{2}\) - \(\dfrac{3}{7}\) = \(\dfrac{57}{14}\)
b : = > x = \(\dfrac{7}{5}\) x\(\dfrac{5}{7}\) = 1
c : = > \(\dfrac{11}{3}\) : \(\dfrac{3}{8}\) = \(\dfrac{11}{3}\) x \(\dfrac{8}{3}\) = \(\dfrac{88}{9}\)
a) \(\dfrac{8}{x}+\dfrac{1}{5}=\dfrac{2}{5}+\dfrac{1}{3}=\dfrac{11}{15}\)
\(\dfrac{8}{x}=\dfrac{11}{15}-\dfrac{1}{5}=\dfrac{8}{15}\)
\(x=\dfrac{8\times15}{8}=15\)
B) \(\left(x-\dfrac{3}{5}\right)=\dfrac{5}{8}\times\dfrac{1}{5}=\dfrac{1}{8}\)
\(x=\dfrac{1}{8}+\dfrac{3}{5}=\dfrac{29}{40}\)
\(a,\dfrac{5}{8}-x=\dfrac{4}{7}\times\dfrac{1}{4}\\ \dfrac{5}{8}-x=\dfrac{4\times1}{7\times4}\\ \dfrac{5}{8}-x=\dfrac{4}{28}\\ \dfrac{5}{8}-x=\dfrac{1}{7}\\ x=\dfrac{5}{8}-\dfrac{1}{7}\\ x=\dfrac{5\times7}{8\times7}-\dfrac{1\times8}{7\times8}\\ x=\dfrac{35}{56}-\dfrac{8}{56}\\ x=\dfrac{35-8}{56}\\ x=\dfrac{27}{56}\\ b,x:\dfrac{4}{5}=\dfrac{3}{4}+\dfrac{1}{6}\\ x:\dfrac{4}{5}=\dfrac{3\times3}{4\times3}+\dfrac{1\times2}{6\times2}\\ x:\dfrac{4}{5}=\dfrac{9}{12}+\dfrac{2}{12}\\ x:\dfrac{4}{5}=\dfrac{9+2}{12}\\ x:\dfrac{4}{5}=\dfrac{11}{12} \\ x=\dfrac{11}{12}\times\dfrac{4}{5}\\ x=\dfrac{11\times4}{12\times5}\\ x=\dfrac{44}{60}=\dfrac{11}{15}\)
a: =>5/8-x=1/7
=>x=5/8-1/7=35/56-8/56=27/56
b: =>x:4/5=9/12+2/12=11/12
=>x=11/12*4/5=44/48=11/12
a: \(\Leftrightarrow x=\dfrac{33}{20}:\dfrac{11}{8}=\dfrac{33}{20}\cdot\dfrac{8}{11}=3\cdot\dfrac{2}{5}=\dfrac{6}{5}\)
b: \(\Leftrightarrow x=5:\dfrac{4}{7}=\dfrac{35}{4}\)
Câu 3:
Chiều rộng là 90x3/5=54(m)
Chu vi là (90+54)x2=288(m)
Câu 4:
Chiều rộng là 60x3/5=36(m)
Chu vi là (60+36)x2=192(m)
Diện tích là 60x36=2160(m2)
