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\(=\dfrac{12}{25}+\dfrac{15}{25}+\dfrac{12}{25}=\left(\dfrac{12}{25}+\dfrac{12}{25}\right)+\dfrac{15}{25}=\dfrac{24}{25}+\dfrac{15}{25}=\dfrac{39}{25}\)
\(\dfrac{13}{7}+\dfrac{5}{6}+\dfrac{2}{7}+\dfrac{7}{6}=\dfrac{15}{7}+\dfrac{12}{6}=\dfrac{29}{7}\)
\(\dfrac{1}{2}\times\dfrac{5}{6}+\dfrac{1}{2}\times\dfrac{11}{6}=\dfrac{1}{2}\times\left(\dfrac{5}{6}+\dfrac{11}{6}\right)=\dfrac{1}{2}\times\dfrac{16}{6}=\dfrac{4}{3}\)
\(\dfrac{9}{5}+\dfrac{5}{7}+\dfrac{7}{5}+\dfrac{3}{7}=\left(\dfrac{9}{5}+\dfrac{7}{5}\right)+\left(\dfrac{5}{7}+\dfrac{3}{7}\right)=\dfrac{16}{5}+\dfrac{8}{7}=\dfrac{112}{35}+\dfrac{40}{35}=\dfrac{152}{35}\)
\(\dfrac{1}{2}\times\dfrac{45}{33}\times\dfrac{1}{9}\times\dfrac{11}{6}=\dfrac{1}{2}\times\dfrac{15}{11}\times\dfrac{1}{9}\times\dfrac{11}{6}=\left(\dfrac{1}{2}\times\dfrac{1}{9}\right)\times\left(\dfrac{15}{11}\times\dfrac{11}{6}\right)=\dfrac{1}{18}\times\dfrac{15}{6}=\dfrac{5}{36}\)
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
dấu . là nhân hay là phần ngăn cách ở hàng phần nghìn thế
a) \(28400:\left(100\times311-310\times100\right)\)
\(=28400:\left[\left(311-310\right)\times100\right]\)
\(=28400:100\)
\(=284\)
b) \(\dfrac{5}{11}+\dfrac{19}{15}+\dfrac{6}{11}+\dfrac{11}{16}+\dfrac{6}{15}+\dfrac{5}{16}\)
\(=\left(\dfrac{5}{11}+\dfrac{6}{11}\right)+\left(\dfrac{19}{15}+\dfrac{6}{15}\right)+\left(\dfrac{11}{16}+\dfrac{5}{16}\right)\)
\(=1+\dfrac{5}{3}+1\)
\(=\dfrac{8}{3}+1\)
\(=\dfrac{11}{3}\)
6/4 x 45/10 + 105/10 : 2/3 - 3/2 x 5
= 3/2 x 45/10 + 105/10 x 3/2 - 3/2 x 5
= 3/2 x (45/10 + 105/10 - 5)
= 3/2 x 10
= 15
\(a,=\left(\dfrac{3}{5}+\dfrac{3}{5}+\dfrac{6}{5}\right)\times\left(\dfrac{6}{7}:7\right)=3\times\dfrac{6}{49}=\dfrac{18}{49}\)
\(\dfrac{15}{18}+\dfrac{8}{23}+\dfrac{3}{18}+\dfrac{15}{23}=\left(\dfrac{15}{18}+\dfrac{3}{18}\right)+\left(\dfrac{8}{23}+\dfrac{15}{23}\right)=1+1=2\)
\(\dfrac{15}{18}+\dfrac{8}{23}+\dfrac{3}{18}+\dfrac{15}{23}\)
\(=(\dfrac{15}{18}+\dfrac{3}{18})+(\dfrac{8}{23}+\dfrac{15}{23})\)
\(=1+1\)
\(=2\)
30/6+ 5/5=5+1=6
6
\(\dfrac{1}{6}+\dfrac{3}{5}+\dfrac{11}{6}+\dfrac{2}{5}+\dfrac{18}{6}\)
\(=\left(\dfrac{1}{6}+\dfrac{11}{6}+\dfrac{18}{6}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)\)
\(=5+1\)
\(=6\)
\(=\left(\dfrac{1}{6}+\dfrac{11}{6}+\dfrac{18}{6}\right)+\left(\dfrac{3}{5}+\dfrac{2}{3}\right)\)
\(=5+1\)
\(=6\)
\(\dfrac{1}{6}+\dfrac{3}{5}+\dfrac{11}{6}+\dfrac{2}{5}+\dfrac{18}{6}\)
= \(\left(\dfrac{1}{6}+\dfrac{11}{6}+\dfrac{18}{6}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)\)
= \(\left(\dfrac{12}{6}+\dfrac{18}{6}\right)+1\)
= \(5+1\)
= \(6\)
6