1) 1/5 . 5/4 + 1/5 . 5/4
= (1/5 + 1/5) . 5/4
= 1/5 . 5/4
= 1/4
2)tự làm
1.\(\frac{1}{5}\times\frac{5}{4}+\frac{1}{5}\times\frac{5}{4}\)
\(=\frac{1}{5}\times\frac{5}{4}\times2\)
\(=\frac{1\times5\times2}{5\times4}\)
\(=\frac{1}{2}\)
2.\(\frac{7}{6}\times\frac{2}{5}-\frac{1}{3}\times\frac{2}{5}+\frac{5}{6}\times\frac{2}{5}\)
\(=\frac{2}{5}\times\left(\frac{7}{6}-\frac{1}{3}+\frac{5}{6}\right)\)
\(=\frac{2}{5}\times\left(\frac{7}{6}-\frac{2}{6}+\frac{5}{6}\right)\)
\(=\frac{2}{5}\times\frac{5}{3}\)
\(=\frac{2}{3}\)
\(\frac{1}{5}x\frac{5}{4}+\frac{1}{5}x\frac{5}{4}=\frac{1}{5}x\left(\frac{5}{4}+\frac{5}{4}\right)=\frac{1}{5}x\frac{10}{4}=\frac{10}{20}=\frac{1}{2}\)
\(\frac{7}{6}x2x5-\frac{1}{3}x\frac{2}{5}+\frac{5}{6}x\frac{2}{5}=\frac{7}{6}x\frac{2}{1}x\frac{5}{1}-\frac{1}{3}x\frac{2}{5}+\frac{5}{6}x\frac{2}{5}=\frac{70}{6}-\frac{2}{15}+\frac{10}{30}\)
\(=\frac{350}{30}-\frac{4}{30}+\frac{10}{30}\)
\(=\frac{346}{30}+\frac{10}{30}\)
\(=\frac{356}{30}\)
Bài số 2 bạn tự rút gọn nha
\(1)\frac{1}{5}\times\frac{5}{4}+\frac{1}{5}\times\frac{5}{4}\)
\(=\left(\frac{1}{5}\times\frac{5}{4}\right)\times2\)
\(=\frac{5}{20}\times2\)
\(=\frac{10}{20}\)
\(=\frac{1}{2}\)
\(2)\frac{7}{6}\times\frac{2}{5}-\frac{1}{3}\times\frac{2}{5}+\frac{5}{6}\times\frac{2}{5}\)
\(=\frac{2}{5}\times\left(\frac{7}{6}-\frac{1}{3}+\frac{5}{6}\right)\)
\(=\frac{2}{5}\times\left(\frac{7}{6}-\frac{2}{6}+\frac{5}{6}\right)\)
\(=\frac{2}{5}\times\left(\frac{5}{6}+\frac{5}{6}\right)\)
\(=\frac{2}{5}\times\frac{10}{6}\)
\(=\frac{20}{30}\)
\(=\frac{2}{3}\)
