\(\frac{(1.09-0.29)\times1\frac{1}{4}}{(18.9-16\frac{13}{20})\times\frac{8}{9}}\)
các anh ,chị giải chi tiết , rõ ràng cho em nha , em cần gấp lắm:
Bải 1 : tính
A= \(\frac{\left(1.09-0.29\right)\cdot1\frac{1}{4}}{18.9-16\frac{13}{20}\cdot\frac{8}{9}}\)
B= 2002/ \(\left(\frac{0.4-\frac{2}{9}+\frac{2}{11}}{1.4-\frac{7}{9}+\frac{7}{11}}\cdot\frac{-1\frac{1}{6}+0,875-0,7}{\frac{1}{3}-0,25+\frac{1}{5}}\right)\)
\(ChoA=\left[0,8.7+\left(0,8\right)^2\right]\left(1,25.7-\frac{4}{5}.1,25\right)+31,64\)
\(B=\frac{\left(1.09-0.29\right).\frac{5}{4}}{\left(18.9-16.65\right).\frac{8}{9}}\)
Hỏi A gấp mấy lần B?
\(A=\left[0,8.7\left(0,8\right)^2\right].\left(1,25.7-\frac{4}{5}.1,25\right)+31,64\)
\(=0,8.\left(7+0,8\right).1,25.\left(7-0,8\right)+31,64\)
\(=0,8.7,8.1,25.6,2+31,64\)
\(=6,24.7,75+31,64\)
\(=48,36+31,64=80\)
\(B=\frac{\left(1,09-0,29\right).\frac{5}{4}}{\left(18,9-16,65\right).\frac{8}{9}}=\frac{0,8.1,25}{2,25.\frac{8}{9}}=\frac{1}{2}\)
\(A:B=80:\frac{1}{2}=160\)
Vậy A gấp 160 lần B.
so sánh A và B biết:
A=\(\left[0.8\cdot7+\left(0.8\right)^2\right]\cdot\left(1.25\cdot7-\frac{4}{5}\cdot1.25\right)-47.86\)
B=\(\frac{\left(1.09-0.29\right)\cdot\frac{5}{4}}{\left(18.9-16.65\right)\cdot\frac{8}{9}}\)
\(A=\left[0,8\cdot7+(0,8)^2\right]\cdot\left[1,25\cdot7-\frac{4}{5}\cdot1,25\right]-47,86\)
\(=0,8\cdot(7+0,8)\cdot1,25\cdot(7-0,8)-47,86\)
\(=0,8\cdot7,8\cdot1,25\cdot6,2-47,86\)
\(=48,36-47,86=0,5\)
\(B=\frac{(1,09-0,29)\cdot\frac{5}{4}}{(18,9-16,65)\cdot\frac{8}{9}}=\frac{0,8\cdot1,25}{2,25\cdot\frac{8}{9}}=\frac{1}{2}\)
\(A:B=0,5:\frac{1}{2}=\frac{1}{2}:\frac{1}{2}=\frac{1}{2}\cdot2=1\)
A gấp 1 lần B
??????????????????
tính nhanh: \(1\frac{1}{4}\times1\frac{1}{8}\times1\frac{1}{15}\times1\frac{1}{24}\times1\frac{1}{35}\times...\times1\frac{1}{9800}\)
Rút gọn biểu thức ta được
\(A=1\frac{1}{2}.1\frac{1}{3}....1\frac{1}{2015}\)
\(=\frac{3}{2}.\frac{4}{3}......\frac{2016}{2015}\)
\(=\frac{2016}{2}=1008\)
\(1\frac{1}{3}\times1\frac{1}{4}\times1\frac{1}{5}\times1\frac{1}{6}\times1\frac{1}{7}\times1\frac{1}{8}\times1\frac{1}{9}\times1\frac{1}{10}\times1\frac{1}{11}\)
\(1\frac{1}{3}.1\frac{1}{4}.1\frac{1}{5}.1\frac{1}{6}.1\frac{1}{7}.1\frac{1}{8}.1\frac{1}{9}.1\frac{1}{10}.1\frac{1}{11}\)
\(=\frac{4}{3}.\frac{5}{4}.\frac{6}{5}.\frac{7}{6}.\frac{8}{7}.\frac{9}{8}.\frac{10}{9}.\frac{11}{10}.\frac{12}{11}\)
\(=\frac{12}{3}=4\)
Tính nhanh \(1\frac{1}{15}\times1\frac{1}{16}\times1\frac{1}{17}\times...\times1\frac{1}{2009}\times1\frac{1}{2010}\)
\(=\frac{16}{15}\times\frac{17}{16}\times\frac{18}{17}\times...\times\frac{2010}{2009}\times\frac{2011}{2010}\)
\(=\frac{1}{15}\times2011\)
\(=\frac{2011}{15}\)
tính nhanh: \(1\frac{1}{13}\times1\frac{1}{14}\times1\frac{1}{15}\times....\times1\frac{1}{2013}\times1\frac{1}{2014}=?\)
1 1/13 x 1 1/14 x ........... x 1 1/2014 = 14/13 x 15/14 x ...... x 2015/2014 = (14 x 15 x ....x 2014) x 2015/( 14 x 15 x .......x2014) x 13 = 2015/13
N = \(1\frac{1}{3}\times1\frac{1}{8}\times1\frac{1}{15}\times1\frac{1}{24}\times...\times1\frac{1}{99}\)