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2/5 + 3/4 7/12 - 2/7 + 1/12 12/17 - 5/17 - 4/17
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14 tháng 4 2016
2/5 + 3/4 = 23/40
7/12 - 2/7 + 1/12 = 25/84 + 1/12 = 8/21
12/17 - 5/17 - 4/17 = 3/17
OK
14 tháng 4 2016
\(\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=\left(\frac{7}{12}+\frac{1}{12}\right)-\frac{2}{7}=\frac{2}{3}-\frac{2}{7}=\frac{14}{21}-\frac{6}{21}=\frac{8}{21}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}=\frac{12-5-4}{17}=\frac{3}{17}\)
HN
2
TN
18 tháng 4 2018
a) 2/5+3/4=23/20
7/12-2/7+1/12=8//21
12/17-5/17-4/17=3/17
b) 675,39+342,14=1017,53
563,87+403,13-328,35=638,65
18 tháng 4 2018
a) 2/5+3/4
=8/20+15/20
=21/20
7/12-2/7+1/12
=7/12+1/12-2/7
=1/4-2/7
=7/28-8/28
=-1/28
12/17-5/17-4/17
=12/17-9/17
=3/17
b) 675,39+342,14
= 1017,53
563,87+403,13-328,35
= 967-328,35
= 638,65
NT
2
PJ
9 tháng 4 2016
2 - 5/6 = 2/1 - 5/6 = 12/6 - 5/6 = 12-5/ 6= 7/6
7/8 + 3/4 = 7/8 + 6 / 8 = 7+8/8 = 15/8
2/5 + 3/4 = 8/20 + 15/20 = 8+15/20 = 23/20
9 tháng 4 2016
2 - 5/6 = 2/1 - 5/6 = 12/6 - 5/6 = 12-5/6 = 7/6
7/8 + 3/4 = 7/8 + 6/8 = 7 + 8/8 =15/8
2/5 + 3/4 = 8/20 + 15/20 = 8 + 15/20 = 23/20
XO
7 tháng 5 2019
A =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\) B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\) C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\) D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)
= \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\) =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\) = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\) = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)
=\(\frac{4}{7}\times1\) = \(1\times\frac{12}{17}\) = \(1:\frac{6}{7}\) = \(\frac{9\times9\times12}{12\times7\times19}\)
=\(\frac{4}{7}\) = \(\frac{12}{17}\) =\(\frac{7}{6}\) = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)
6 tháng 4 2017
2 - 5/6= 7/6
7/8+3/4=`13/8
2/5+3/4=23/20
7/12 - 2/7 + 1/12=8/21
12/17 - 5/17 - 4/17=3/17
7 tháng 2 2022
Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
10 tháng 4 2018
2/5 +3/4=23/20 7/12 - 2/7 +1/12=32/84 12/17 -5/17 - 4/17=3/17
675,39 + 342,14=1017,54 563,87 + 203,13 - 328,35 =438,65
12 tháng 3 2022
a: =(5/7+2/7)+(4/3+5/3)=3+1=4
b: =(17/12+7/12)+(29/7-8/7)
=2+3=5
c: =(2/5+3/5)+(6/9+1/3)+(7/4+1/4)
=1+2+1
=4
d: =(1/3+2/3)+(13/17+4/17)+(29/11+4/11)
=1+1+3=5
12 tháng 10 2021
Câu 2:
\(\dfrac{7}{9}\cdot\dfrac{3}{35}=\dfrac{1}{5}\cdot\dfrac{1}{3}=\dfrac{1}{15}\)
\(\dfrac{9}{22}\cdot55=\dfrac{9\cdot55}{22}=\dfrac{9\cdot5}{2}=\dfrac{45}{2}\)
a)\(\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)
b)\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=\frac{7}{12}+\frac{1}{12}-\frac{2}{7}\)\(=\frac{8}{12}-\frac{2}{7}=\frac{56}{84}-\frac{24}{84}=\frac{32}{84}=\frac{8}{21}\)
c) \(\frac{12}{17}-\frac{5}{17}-\frac{3}{17}=\frac{12-5-3}{17}=\frac{4}{17}\)
Chúc bạn học tốt !