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a) 5x7x8x9x10 / 7x8x9x10x11=5/11
b) 3x145+3x55 / 6x215+6x85=3x(145+55)/6x(215+85)=3x200/6x300=3x100x2/3x2x100x3=1/3
\(\frac{5\times7\times8\times9\times10}{7\times8\times9\times10\times11}\)
\(=\frac{5\times\left(7\right)\times\left(8\right)\times\left(9\right)\times\left(10\right)}{\left(7\right)\times\left(8\right)\times\left(9\right)\times\left(10\right)\times11}\)
\(=\frac{5}{11}\)
\(\frac{3\times145+3\times55}{6\times215+6\times85}\)
\(=\frac{3\times\left(145+55\right)}{6\times\left(215+85\right)}\)
\(=\frac{3\times200}{6\times300}\)
\(=\frac{600}{1800}=\frac{1}{3}\)
\(\frac{5\times7\times8\times9\times10}{7\times8\times9\times10\times11}=\frac{5}{11}\)
\(\frac{3\times145+3\times55}{6\times215+6\times85}\)
\(=\frac{3\times\left(145+55\right)}{6\times\left(215+85\right)}\)
\(=\frac{3\times200}{6\times300}\)
\(=\frac{3\times2\times100}{3\times2\times3\times100}\)
\(=\frac{1}{3}\)
bài 4:so sánh
5/2 lớn hơn 3/7
4/3 lớn hơn,3/2 lớn hơn
bài 6:rút gọn các phân số sau:
3/9=1/3 9/12=3/4 8/18=4/9 60/36=10/6 17/34=1/2 17/51=1/3 35/100=7/20 25/100=1/4 8/1000=1/125 24/30=4/5 18/54=1/3 72/42=12/7
đay nhé mk chưa làm hết đc bn viết liền quá mk nhìn khó mà mk hỏi bài 7 là nhân hay cộng vậy?
\(\dfrac{1}{2}+\dfrac{5}{6}+\dfrac{11}{12}+\dfrac{19}{20}+\dfrac{29}{30}+\dfrac{41}{42}+\dfrac{55}{56}+\dfrac{71}{72}+\dfrac{89}{90}=1-\dfrac{1}{2}+1-\dfrac{1}{6}+1-\dfrac{1}{12}+....+1-\dfrac{1}{90}=1+1+...+1-\left(\dfrac{1}{2}+\dfrac{1}{6}+...+\dfrac{1}{90}\right)=9-\left(\dfrac{1}{1x2}+\dfrac{1}{2x3}+...+\dfrac{1}{9x10}\right)=9-\left(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+....+\dfrac{1}{9}-\dfrac{1}{10}\right)=9-\left(1-\dfrac{1}{10}\right)=9-\dfrac{9}{10}=\dfrac{81}{10}\)
Bài làm :
1)\(\frac{3}{2}+\frac{5}{2}-\frac{4}{2}=\frac{3+5-4}{2}=\frac{4}{2}=2\)
2)\(\frac{2}{5}\times\frac{1}{2}\div\frac{1}{3}=\frac{2\times1\times3}{5\times2\times1}=\frac{6}{10}=\frac{3}{5}\)
3)\(\frac{2}{9}\div\frac{9}{2}\times\frac{1}{2}=\frac{2\times2\times1}{9\times9\times2}=\frac{4}{162}=\frac{2}{81}\)
4)\(\left(\frac{4}{11}+\frac{3}{11}\right)\times\frac{2}{6}=\frac{4+3}{11}\times\frac{2}{6}=\frac{7}{11}\times\frac{2}{6}=\frac{7\times2}{11\times6}=\frac{14}{66}=\frac{7}{33}\)
\(\frac{3}{2}\)\(+\)\(\frac{5}{2}\)\(-\)\(\frac{4}{2}\)\(=\)\(\left(\frac{3}{2}+\frac{5}{2}\right)-\frac{4}{2}\)
\(=\frac{8}{2}-\frac{4}{2}=\frac{4}{2}=2\)
\(\frac{2}{5}\)\(x\)\(\frac{1}{2}\)\(:\)\(\frac{1}{3}\)\(=\)\(\left(\frac{2}{5}x\frac{1}{2}\right)\)\(:\)\(\frac{1}{3}\)
\(=\)\(\frac{2}{10}\)\(:\)\(\frac{1}{3}\)\(=\frac{2}{10}x\frac{3}{1}\)\(=\frac{6}{10}=\frac{3}{5}\)
\(\frac{3\times145+3\times55}{6\times215+6\times85}\)
\(=\frac{3\times\left(145+55\right)}{6\times\left(215+85\right)}\)
\(=\frac{3\times200}{6\times300}\)
\(=\frac{600}{1800}=\frac{1}{3}\)
#Fox