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a, \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac{1}{5}\)
\(=\frac{5}{11}\times\frac{7}{25}+\frac{5}{11}\times\frac{3}{5}\)
\(=\frac{5}{11}\times\left(\frac{7}{25}+\frac{3}{5}\right)\)
\(=\frac{5}{11}\times\frac{22}{25}\)
\(=\frac{2}{5}\)
b, \(\frac{3}{7}\times\frac{25}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\frac{75}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\left(\frac{75}{19}-\frac{18}{19}\right)\)
\(=\frac{1}{7}\times3\)
\(=\frac{3}{7}\)
\(a,2\times134\times50\)
\(=\left(2\times50\right)\times134\)
\(=100\times134\)
\(=13400\)
\(b,397\times20+397\times82-397\times2\)
\(=397\times\left(20+82-2\right)\)
\(=397\times100\)
\(=39700\)
1. Câu hỏi kêu tìm số không rõ nên không giải được!
2. 705 dư 31
\(15x\frac{2121}{4343}+15x\frac{222222}{434343}\)
\(=15x\frac{21}{43}+15x\frac{22}{43}\)
\(=15x\left(\frac{21}{43}+\frac{22}{43}\right)\)
\(=15x1\)
\(=15\)
= 15 x 21/43 + 15x 22/43
= 15 x (21/43 + 22/43)
= 15 x 1 =15
a) \(\frac{13}{19}+\frac{18}{19}+\frac{19}{19}=\left(\frac{13}{19}+\frac{17}{19}\right)+\frac{18}{19}=\frac{20}{19}+\frac{18}{19}=\frac{48}{19}\)
b) \(\frac{3}{5}+\frac{3}{16}+\frac{13}{16}=\left(\frac{3}{16}+\frac{13}{16}\right)+\frac{3}{5}=1+\frac{3}{5}=\frac{5}{5}+\frac{3}{5}=\frac{8}{5}\)
a) \(\frac{13}{19}+\frac{18}{19}+\frac{17}{19}\)
= \(\frac{31}{19}+\frac{17}{19}\)
= \(\frac{48}{19}.\)
b) \(\frac{3}{5}+\frac{3}{16}+\frac{13}{16}\)
= \(\frac{3}{5}+\left(\frac{3}{16}+\frac{13}{16}\right)\)
= \(\frac{3}{5}+\frac{16}{16}\)
= \(\frac{3}{5}+1\)
= \(\frac{3}{5}.\)
= 705 x (82 + 19 - 1)
= 705 x 100
= 70500
705 x 82 + 705 x 19 - 705 x 1
= 705 x ( 82 + 19 - 1 )
= 705 x 100
= 70500