( 11)/20: 5 1/2-2,4 .35%
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a) \(2\dfrac{4}{9}+6\dfrac{7}{11}+7\dfrac{5}{9}+13\dfrac{4}{11}\)
\(=2+\dfrac{4}{9}+6+\dfrac{7}{11}+7+\dfrac{5}{9}+13+\dfrac{4}{11}\)
\(=\left(2+6+7+13\right)+\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\left(\dfrac{7}{11}+\dfrac{4}{11}\right)\)
\(=28+1+1\)
\(=30\)
b) \(\dfrac{3}{4}+\dfrac{1}{2}\times\dfrac{12}{5}-1\dfrac{1}{2}\)
\(=\dfrac{3}{4}+\dfrac{1}{2}-1-\dfrac{1}{2}\)
\(=\dfrac{3}{4}-1\)
\(=\dfrac{3}{4}-\dfrac{4}{4}\)
\(=-\dfrac{1}{4}\)
6,35 x X + 1,25 x X + 2,4 x X = 20
X x (6,35 + 1,25 + 2,4) = 20
X x 10 = 20
x = 2
\(A=\left(\dfrac{5}{12}.\dfrac{21}{15}\right):\dfrac{1}{4}\)
\(=\dfrac{7}{12}:\dfrac{1}{4}\)
\(=\dfrac{28}{12}=\dfrac{7}{3}\)
\(B=\left(\dfrac{2}{7}:\dfrac{5}{4}\right).\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\dfrac{5}{16}\)
\(=\dfrac{1}{14}\)
\(C=\left(\dfrac{11}{15}.\dfrac{35}{44}\right).\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\dfrac{4}{91}\)
\(=\dfrac{1}{39}\)
\(D=\left(\dfrac{7}{20}+\dfrac{11}{15}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\left(\dfrac{13}{12}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\dfrac{-1}{36}\)
\(=6\)
\(d,\dfrac{1}{2}+\dfrac{4}{3}=\dfrac{3}{6}+\dfrac{8}{6}=\dfrac{3+8}{6}=\dfrac{11}{6}\)
\(e,\dfrac{6}{7}+\dfrac{11}{4}=\dfrac{24}{28}+\dfrac{77}{28}=\dfrac{24+77}{28}=\dfrac{101}{28}\)
\(g,\dfrac{9}{5}+\dfrac{7}{4}=\dfrac{36}{20}+\dfrac{35}{20}=\dfrac{36+35}{20}=\dfrac{71}{20}\)
\(h,\dfrac{2}{8}+\dfrac{1}{4}=\dfrac{2}{8}+\dfrac{2}{8}=\dfrac{2+2}{8}=\dfrac{4}{8}=\dfrac{1}{2}\)
\(i,\dfrac{3}{20}+\dfrac{2}{5}=\dfrac{3}{20}+\dfrac{8}{20}=\dfrac{3+8}{20}=\dfrac{11}{20}\)
\(k,\dfrac{6}{35}+\dfrac{2}{7}=\dfrac{6}{35}+\dfrac{10}{35}=\dfrac{6+10}{35}=\dfrac{16}{35}\)
Ta có: \(\frac{11}{20}:5\frac{1}{2}-2,4\cdot35\%\)
\(=\frac{11}{20}\cdot\frac{2}{11}-\frac{24}{10}\cdot\frac{35}{100}\)
\(=\frac{2}{20}-\frac{21}{25}\)
\(=\frac{10}{100}-\frac{84}{100}=\frac{-74}{100}=\frac{-37}{50}\)