=27.(18+103-120)/33.(15+12)
= 27.1/33.27
=1/33
\(=\frac{27\left(18+103-120\right)}{33\left(15+12\right)}\)
\(=\frac{27\times1}{33\times27}\)
\(=\frac{1}{33}\)
\(\frac{27\cdot18+27\cdot103-27\cdot102}{15.33+33\cdot12}\)
\(\frac{27\times18+27\times103-120\times27}{15\times33+33\times12}\)
\(A=\frac{7}{10\cdot11}+\frac{7}{11\cdot12}+\frac{7}{12\cdot13}+...+\frac{7}{69\cdot70}\)
\(B=\frac{1}{25\cdot27}+\frac{1}{27\cdot29}+\frac{1}{29\cdot30}+...+\frac{1}{73\cdot75}\)
\(C=\frac{4}{2\cdot4}+\frac{4}{4\cdot6}+\frac{4}{6\cdot8}+...3+\frac{4}{2008\cdot2010}\)
Tính nhanh:
27 . 18 +27 .103 -120 . 27
15 . 33 + 33 . 12
Tính \(\frac{M}{N}\)biết :
M = \(\frac{2}{7\cdot19}+\frac{6}{7\cdot27}+\frac{1}{4\cdot9}+\frac{7}{12\cdot43}+\frac{8}{17\cdot43}\)
N = \(\frac{9}{7\cdot19}+\frac{5}{7\cdot33}+\frac{7}{10\cdot33}+\frac{11}{10\cdot31}\)
H=\(\frac{1\cdot2\cdot3+2\cdot4\cdot6+3\cdot6\cdot9+5\cdot10\cdot15}{1\cdot3\cdot6+2\cdot6\cdot12+3\cdot9\cdot18+5\cdot15\cdot30}\)= ?
Giá trị của biểu thức \(C=\frac{1\cdot5\cdot6+2\cdot10\cdot12+4\cdot20\cdot24+...+9\cdot45\cdot54}{1\cdot3\cdot5+2\cdot6\cdot10+4\cdot12\cdot20+...+9\cdot27\cdot45}\) là \(C=\)
E=\(\frac{1}{1\cdot101}+\frac{1}{2\cdot102}+\frac{1}{3\cdot103}+...+\frac{1}{10\cdot110}\)và F=\(\frac{1}{1\cdot11}+\frac{1}{2\cdot12}+\frac{1}{3\cdot13}+...+\frac{1}{100\cdot110}\)
tính tỉ số\(\frac{E}{F}\)
tính nhanh
\(\frac{1\cdot5\cdot6+2\cdot10\cdot12+4\cdot20\cdot24+9\cdot45\cdot54}{1\cdot3\cdot5+2\cdot6\cdot10+4\cdot2\cdot20+9\cdot27\cdot45}\)
