tính bằng cách thuật tiện nhất : 7/19x1/3+7/19x2/3
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\(\frac{3}{5}x\frac{8}{27}x\frac{5}{3}=\frac{3}{3}x\frac{5}{5}x\frac{8}{27}=\frac{8}{27}\)
\(\frac{7}{19}x\frac{1}{3}+\frac{7}{19}x\frac{2}{3}=\frac{7}{19}x\left(\frac{1}{3}+\frac{2}{3}\right)=\frac{7}{19}\)
a) \(\frac{2}{9}+\frac{1}{5}+\frac{7}{9}+\frac{4}{5}=\left(\frac{2}{9}+\frac{7}{9}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)= 1+1=2 \)
b) \(\frac{19}{37}+\left(1+\frac{19}{37}\right)=\left(\frac{19}{37}-\frac{19}{37}\right)+1=0+1=1\)
c) \(\frac{9}{8}-\left(\frac{17}{7}-\frac{3}{7}\right)+\frac{7}{8}=\frac{9}{8}+\frac{7}{8}-\left(\frac{17}{7}-\frac{3}{7}\right)=2-2=0\)
d) \(\frac{3}{5}\times\frac{8}{27}\times\frac{5}{3}=\frac{3}{5}\times\frac{5}{3}\times\frac{8}{27}=1\times\frac{8}{27}=\frac{8}{27}\)
e) \(\frac{7}{19}\times\frac{1}{3}+\frac{7}{19}\times\frac{2}{3}=\frac{7}{19}\times\left(\frac{1}{3}+\frac{2}{3}\right)=\frac{7}{19}\times1=\frac{7}{19}\)
f) \(\frac{12}{5}\times4-4\times\frac{7}{5}=4\times\left(\frac{12}{5}-\frac{7}{5}\right)=4\times1=4\)
a, \(=\left(\dfrac{4}{7}+\dfrac{3}{7}\right)+\left(\dfrac{3}{5}+\dfrac{3}{5}\right)=1+\dfrac{6}{5}=\dfrac{5+6}{5}=\dfrac{11}{5}\)
\(\dfrac{7}{19}\times\dfrac{1}{3}+\dfrac{7}{13}\times\dfrac{2}{3}\)
\(=\dfrac{7}{19}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)
\(=\dfrac{7}{19}\times1\)
\(=\dfrac{7}{19}\)
\(=\dfrac{2}{5}\cdot\dfrac{7}{3}\cdot\dfrac{3}{7}\cdot\dfrac{5}{2}+2020=1+2020=2021\)
7/19 . 1/3 + 7/19 . 2/3 =7/19 .(1/3 + 2/3)= 7/19 . 1 = 7/19
7/19x⅓+7/19x2/3