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\(12.57+57.15+63.57\\ \Rightarrow57.\left(12+15+63\right).\\ \Rightarrow57.90=5130.\)
a) 34.15 + 34.85 = 34.(15+85) = 34.100 = 3400
b) 12.57 + 57.25 + 63.57 = 57.(12+25+63) = 57.100 = 5700
c) 36.28 + 36.82 + 64.69 + 64.41 = 36.(28+82) + 64(69+41) = 36.110 + 64.110 = 110.(36+64) = 11000
d) 2.31.12 + 4.6.42 + 8.27.3 = 24.31 + 24.42 + 24.27 = 24.(31+42+27) = 24.100 = 2400
57.43 + 12.57 + 55.43
= [57.43 + 12.57] + 55.43
= 70.00 + 55.43
= 125.43
\(=5.22\left(3134+275\cdot2+1.079\cdot4\right)\)
\(=5.22\cdot3688.316=19253.00952\)
\(1\dfrac{13}{15}.0,75-\left(\dfrac{11}{20}+25\%\right):\dfrac{3}{7}\)
\(\Leftrightarrow\) \(\left\{{}\begin{matrix}=\dfrac{28}{15}.\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{1}{4}\right):\dfrac{7}{3}\\=\dfrac{7}{5}-\dfrac{4}{5}.\dfrac{3}{7}\\=\dfrac{7}{5}-\dfrac{12}{35}\\=\dfrac{37}{35}\end{matrix}\right.\)\(\Rightarrow\) \(kết\) \(quả\) \(=\dfrac{37}{35}\)
\(\Rightarrow C=\left(-\dfrac{3}{4}\right)\cdot\left(-\dfrac{8}{9}\right)\cdot\left(-\dfrac{15}{16}\right)\cdot\cdot\cdot\cdot\left(-\dfrac{399}{400}\right)\)
\(=-\left(\dfrac{3}{4}\cdot\dfrac{8}{9}\cdot\dfrac{15}{16}\cdot\cdot\cdot\cdot\dfrac{399}{400}\right)\)
\(=-\left(\dfrac{1\cdot3}{2\cdot2}\cdot\dfrac{2\cdot4}{3\cdot3}\cdot\dfrac{3\cdot5}{4\cdot4}\cdot\cdot\cdot\cdot\dfrac{19\cdot21}{20\cdot20}\right)\)
\(=-\left(\dfrac{1\cdot2\cdot3\cdot4\cdot...\cdot19}{2\cdot3\cdot4\cdot...\cdot20}\cdot\dfrac{3\cdot4\cdot5\cdot...\cdot21}{2\cdot3\cdot4\cdot...\cdot20}\right)\)
\(=-\left(\dfrac{1}{20}\cdot\dfrac{21}{2}\right)=-\dfrac{21}{40}\)
12,57 + 57,15 + 63,15
= 12,57 + (57,15 + 63,15)
= 12,57 + 120,3
= 132,87
\(12.57+57.15+63.15\)
\(=12.57+15.\left(57+63\right)\)
\(=12.57+15.120\)
\(=12.57+15.10.12\)
\(=12.57+150.12\)
\(=12.\left(57+150\right)\)
\(=12.207\)
\(=2484\)