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Ta có:
\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)........\left(1-\frac{1}{2017}\right).\left(1-\frac{1}{2018}\right)\)
\(\Rightarrow B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{2016}{2017}.\frac{2017}{2018}\)
Đởn giản hết sẽ còn là:
\(\Rightarrow B=\frac{1}{2018}\)
7/18 + 5/3 . 12/9 : 55/4
= 7/18 + 20/9 . 4/55
= 7/18 + 16/99
= 693/1782 + 288/1782
= 981/1782
A,\(\frac{7}{13}+\frac{1}{7}+\frac{18}{30}=\frac{49}{91}+\frac{13}{91}+\frac{18}{30}=\frac{62}{91}+\frac{18}{30}=\frac{1860}{2730}+\frac{1638}{2730}=\frac{583}{455}\)
B,\(\left(\frac{20}{21}+\frac{3}{14}\right)-\frac{2}{3}=\left(\frac{280}{294}+\frac{63}{294}\right)-\frac{2}{3}=\frac{7}{6}-\frac{2}{3}=\frac{21}{18}-\frac{12}{18}=\frac{9}{18}=\frac{1}{2}\)
C,\(=\frac{17}{5}+\frac{31}{7}=\frac{119}{35}+\frac{155}{35}=\frac{234}{35}\)
Phân số lớn nhất :\(\frac{9}{10}\)
Phân số bé nhất :\(\frac{1}{2}\)
\(\frac{2}{9}\times\frac{5}{17}+\frac{7}{9}+\frac{2}{9}\times\frac{12}{17}\)
\(=\frac{2}{9}\times\left(\frac{5}{17}+\frac{12}{17}\right)+\frac{7}{9}\)
\(=\frac{2}{9}\times1+\frac{7}{9}\)
\(=\frac{2}{9}+\frac{7}{9}\)
\(=1\)
\(\frac{2}{9}\)× \(\frac{5}{17}\)+ \(\frac{7}{9}\)+\(\frac{2}{9}\)×\(\frac{12}{17}\)
= \(\frac{2}{9}\)×( \(\frac{5}{17}\)+\(\frac{12}{17}\)) + \(\frac{7}{9}\)
= \(\frac{2}{9}\)× \(\frac{17}{17}\)+\(\frac{7}{9}\)
= \(\frac{2}{9}\)+ \(\frac{7}{9}\)
= 1
109
198
\(\frac{7}{18}+\frac{5}{3}\times1\frac{3}{9}\div\frac{55}{4}=\)\(\frac{7}{18}+\frac{5}{3}\times\frac{12}{9}\div\frac{55}{4}=\)\(\frac{7}{18}+\frac{5}{3}\times\frac{12}{9}\times\frac{4}{55}=\)\(\frac{7}{18}+\frac{5\times12\times4}{3\times9\times55}=\)\(\frac{7}{18}+\frac{4\times4}{9\times11}=\)\(\frac{7}{18}+\frac{16}{99}=\)\(\frac{693}{1782}+\frac{288}{1782}=\)\(\frac{981}{1782}=\frac{109}{198}\)