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a, 23/4 : 3 + 9/4 x 1/3 - 3/8
= 7,8 + 12,22 - 3,8
= 20,02 - 3,8
=16,22
b, 3/5 : 5/6 : 6/7 : 7/8 + 2/5 +23/35
=3/5 x 6/5 x 7/6 x 8/7 + 2/5 + 23/35
=24/25 + 2/5 + 23/35
=1/5 x(24/5 + 2 +23/7)
=1/5 x 353/35
=353/175
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Kết quả nè bạn ơi;
A; 3/4 + 2/5=23/20
B;7/4 - 1/2=5/4
C;4/9 x 6/8=24/72
D;14/5 : 7/8=112/35
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\(\frac{4}{2\cdot7}=\frac{4\cdot5}{2\cdot7\cdot5}=\frac{20}{70}\)
\(\frac{11}{7\cdot5}=\frac{11\cdot2}{7\cdot5\cdot2}=\frac{22}{70}\)
\(\frac{9}{2\cdot5}=\frac{9\cdot7}{2\cdot5\cdot7}=\frac{63}{70}\)
=))
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a.7,2 :2 x 58,6 + 2,93 x 2 x 64
= 3,6 x 58,6 + 5,86 x 64
=210,96 + 357,04
=586
b.\(4\frac{2}{5}+2\frac{3}{7}-2\frac{2}{5}+5\frac{4}{7}\)
=\(\left(4\frac{2}{5}-2\frac{2}{5}\right)+\left(2\frac{3}{7}+5\frac{4}{7}\right)\)
= 2 + 8
= 10
c. 2 x 41 x 36 + 8 x 9 x 58 + 12 x 6
=72 x 41 + 72 x 58 + 72 x 1
=72 x ( 41 + 58 +1 )
=72 x 100
=7200
d, \(\frac{3}{5}\)x \(\frac{1}{2}\):\(\frac{2}{5}\)
=\(\frac{3}{5}\)x \(\frac{1}{2}\)x\(\frac{5}{2}\)
=\(\frac{3}{4}\)
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a)x : 3 - 7 * 2 = 1,56
x : 3 - 14 = 1,56
x : 3 = 1,56 + 14
x : 3 = 15,56
x = 15,56 * 3
x = 46,68
b)nếu dấu chấm trên đề là dấu phẩy thì:
x : 6,4 = 1,248
x = 1,248 * 6,4
x = 7,9872
c)(x + 1) + (x + 2) + (x + 3) + (x + 4) + (x + 5) = 40
x + 1 + x + 2 + x + 3 + x + 4 + x + 5 = 40
(x + x + x + x + x) + (1 + 2 + 3 + 4 + 5) = 40
5 * x + 15 = 40
5 * x = 40 - 15
5 * x = 25
x = 25 : 5
x = 5
A) X:3 - 7 * 2 = 1,56
X:3-14=1,56
X:3=1,56+14
X:3=5,56
X= 5,56* 3 =16,68
B) X : 6 . 4 = 1 ,248
X = 1,248 :4 *6
X=1,872
C) ĐỀ DÀI LÀM LUN
= 5X + (1+2+3+4+5) =40
5X+15 =40
5X= 40-15=25
X= 25:5=5
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\(A=\frac{1}{1.3}-\frac{1}{3.5}+\frac{1}{3.5}-\frac{1}{5.7}+...+\frac{1}{9.11}-\frac{1}{11.13}\)
\(\Leftrightarrow A=\frac{1}{1.3}-\frac{1}{11.13}=\frac{1}{3}-\frac{1}{143}=\frac{140}{429}\)
\(A=\frac{4}{1.3.5}+\frac{4}{3.5.7}+\frac{4}{5.7.9}+\frac{4}{7.9.11}+\frac{4}{9.11.13}\)
\(\Rightarrow A=\frac{1}{1.3}-\frac{1}{3.5}+\frac{1}{3.5}-\frac{1}{5.7}+...+\frac{1}{9.11}-\frac{1}{11.13}\)
\(\Rightarrow A=\frac{1}{1.3}-\frac{1}{11.13}=\frac{1}{3}-\frac{1}{143}=\frac{140}{429}\)
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\(\frac{2}{3}:\frac{x}{5}+\frac{5}{7}=\frac{2}{7}:\frac{3}{5}+\frac{10}{9}\)
\(\frac{2}{3}:\frac{x}{5}+\frac{5}{7}=\frac{10}{21}+\frac{10}{9}\)
\(\frac{2}{3}:\frac{x}{5}+\frac{5}{7}=\frac{100}{63}\)
\(\frac{2}{3}:\frac{x}{5}\) \(=\frac{100}{63}-\frac{5}{7}\)
\(\frac{2}{3}:\frac{x}{5}\) \(=\frac{55}{63}\)
\(\frac{x}{5}\) \(=\frac{2}{3}:\frac{55}{63}\)
\(\frac{x}{5}\) \(=\frac{42}{55}\)
\(\frac{x\cdot11}{55}\) \(=\frac{42}{55}\)
\(\Rightarrow x\cdot11=42\)
\(x\) \(=42:11\)
\(x\) \(=\frac{42}{11}\)
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a) \(\left(\frac{1}{3}+\frac{1}{5}\right)+\left(\frac{1}{6}-\frac{1}{5}\right)=\left(\frac{1}{3}+\frac{1}{6}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)=\frac{1}{2}\)
b) \(\frac{3}{16}\times\frac{7}{5}+\frac{3}{5}\times\frac{9}{16}=\frac{21}{80}+\frac{27}{80}=\frac{48}{80}=\frac{3}{5}\)
c) \(\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{2020\times2021}=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{2020}-\frac{1}{2021}\)
\(=1-\frac{1}{2021}=\frac{2020}{2021}\)
d) \(\frac{1}{1\times3}+\frac{1}{3\times5}+...+\frac{1}{2021\times2023}=\frac{1}{2}\times\left(\frac{2}{1\times3}+\frac{2}{3\times5}+...+\frac{2}{2021\times2023}\right)\)
\(=\frac{1}{2}\times\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2021}-\frac{1}{2023}\right)\)
\(=\frac{1}{2}\times\left(1-\frac{1}{2023}\right)=\frac{1}{2}\times\frac{2022}{2023}=\frac{1011}{2023}\)
e) \(\frac{3}{2}\times\frac{1}{7}\times\frac{5}{4}+\frac{15}{2}\times\frac{6}{7}\times\frac{1}{4}==\frac{15}{56}+\frac{80}{56}=\frac{95}{56}\)
\(\left(\dfrac{5}{7}+x\right)\div\dfrac{4}{9}=\dfrac{2}{3}\)
\(\dfrac{5}{7}+x=\dfrac{2}{3}\times\dfrac{4}{9}\)
\(\dfrac{5}{7}+x=\dfrac{8}{27}\)
\(x=\dfrac{8}{27}-\dfrac{5}{7}\)
\(x=\dfrac{-79}{189}\)