tính nhanh
\(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
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\(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
\(=\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{7}.\dfrac{82}{5}\)
\(=\dfrac{4}{7}.\left(\dfrac{89}{5}-\dfrac{82}{5}\right)\)
\(=\dfrac{4}{7}.\dfrac{7}{5}\)
\(=\dfrac{4}{5}\)
\(\dfrac{5}{7}.\dfrac{-4}{19}+\dfrac{-15}{7}.\dfrac{5}{19}\)
\(=\dfrac{5}{7}.\dfrac{-4}{19}+\dfrac{5}{7}.\dfrac{-15}{19}\)
\(=\dfrac{5}{7}.\left(\dfrac{-4}{19}+\dfrac{-15}{19}\right)\)
\(=\dfrac{5}{7}.\left(-1\right)\)
\(=\dfrac{-5}{7}\)
\(-2\dfrac{1}{4}.\)\(\left(3\dfrac{5}{12}-1\dfrac{2}{9}\right)\)
=\(\dfrac{-9}{4}\).\(\left(\dfrac{41}{12}-\dfrac{11}{9}\right)\)
=\(\dfrac{-9}{4}.\dfrac{41}{12}-\dfrac{-9}{4}.\dfrac{11}{9}\)
=\(\dfrac{-123}{16}-\dfrac{-11}{4}\)
=\(\dfrac{-123}{16}-\dfrac{-44}{16}\)
=\(\dfrac{-79}{16}\)
\(\left(-25\%+0,75+\dfrac{7}{12}\right)\div\left(-2\dfrac{1}{8}\right)\)
=\(\left(\dfrac{-1}{4}+\dfrac{3}{4}+\dfrac{7}{12}\right)\div\left(\dfrac{-17}{8}\right)\)
=\(\left(\dfrac{-3}{12}+\dfrac{9}{12}+\dfrac{7}{12}\right).\dfrac{-8}{17}\)
=\(\dfrac{13}{12}.\dfrac{-8}{17}=\dfrac{-26}{51}\)
\(a,A=\dfrac{\dfrac{5}{4}+\dfrac{5}{5}+\dfrac{5}{7}-\dfrac{5}{11}}{\dfrac{10}{4}+\dfrac{10}{5}+\dfrac{10}{7}-\dfrac{10}{11}}\\ =\dfrac{5.\left(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{11}\right)}{10.\left(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{11}\right)}\\ =\dfrac{5}{10}\\ =\dfrac{1}{2}\)
Vậy \(A=\dfrac{1}{2}\)
\(b,B=\dfrac{2+\dfrac{6}{5}-\dfrac{6}{7}-\dfrac{6}{11}}{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}}\\ =\dfrac{3.\left(\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}\right)}{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}}\\ =3\)
Vậy \(B=3\)
\(1\dfrac{4}{5}+2\dfrac{5}{7}+3\dfrac{4}{5}+4\dfrac{5}{7}\)
\(\text{=}\left(1\dfrac{4}{5}+3\dfrac{4}{5}\right)+\left(2\dfrac{5}{7}+4\dfrac{5}{7}\right)\)
\(\text{=}1+3+\left(\dfrac{4}{5}+\dfrac{4}{5}\right)+2+4+\left(\dfrac{5}{7}+\dfrac{5}{7}\right)\)
\(\text{=}10+\dfrac{8}{5}+\dfrac{10}{7}\text{=}131\dfrac{1}{35}\)
a: \(=\dfrac{-2}{12}-\dfrac{5}{12}+\dfrac{7}{12}=0\)
b: \(=\left(\dfrac{4}{45}-\dfrac{1}{45}+\dfrac{7}{45}+\dfrac{4}{45}-\dfrac{2}{45}-\dfrac{9}{45}\right)=\dfrac{3}{45}=\dfrac{1}{15}\)
Bài 1:
+) \(\dfrac{7}{8}\times y=\dfrac{3}{2}+\dfrac{6}{4}=3\)
\(y=3:\dfrac{7}{8}=\dfrac{24}{7}\)
+) \(\dfrac{1}{y}\times\left(\dfrac{2}{5}+\dfrac{1}{5}\right)=\dfrac{10}{3}\)
\(\dfrac{1}{y}=\dfrac{10}{3}:\dfrac{3}{5}=\dfrac{50}{9}\)
\(y=\dfrac{9}{50}\)
a: =9+7=16
b: =11+3/13-2-4/7-5-3/13
=4-4/7
=28/7-4/7=24/7
c: =2/7(5+1/4-3-1/4)=2/7x2=4/7
1.Tính nhanh:
\(15\dfrac{1}{4}:\left(-\dfrac{5}{7}\right)-25\dfrac{1}{4}:\left(-\dfrac{5}{7}\right)\)
` 15 1/4 : ( - 5/7 ) - 25 1/4 : ( -5/7 ) `
`= 61/4 . (-7)/5 - 101/4 . (-7)/5`
`= (-7)/5 . ( 61/4 - 101/4 )`
`= (-7)/5 . (-40)/4`
`= (-7)/5 . (-10)`
`= 14`
Có:
\(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
\(=\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4.82}{5.7}=\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4.82}{7.5}=\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{7}.\dfrac{89}{5}\)
\(=\dfrac{4}{7}.\left(\dfrac{89}{5}-\dfrac{82}{5}\right)=\dfrac{4}{7}.\dfrac{7}{5}=\dfrac{4}{5}\)
Chúc bạn học tốt!
\(\dfrac{4}{7}\) .\(\dfrac{89}{5}\) - \(\dfrac{4}{5}\). \(\dfrac{82}{7}\)
= \(\dfrac{4.89}{7.5}\) - \(\dfrac{4}{5}\) . \(\dfrac{82}{7}\)= \(\dfrac{4}{5}\) .\(\dfrac{89}{7}\) - \(\dfrac{4}{5}\) . \(\dfrac{82}{7}\)= \(\dfrac{4}{5}\)\(\left(\dfrac{89}{7}-\dfrac{82}{7}\right)\)= \(\dfrac{4}{5}\). 1= \(\dfrac{4}{5}\)