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Bài 1:
câu a: 4\(\dfrac{4}{9}\) : 2\(\dfrac{2}{3}\) + 3\(\dfrac{1}{6}\)
= \(\dfrac{40}{9}\) : \(\dfrac{8}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{5}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{10}{6}\) + \(\dfrac{19}{6}\)
= \(\dfrac{29}{6}\)
b, (15,25 + 3,75) \(\times\) 4 + ( 20,71 + 5,29)\(\times\) 5
= 19 \(\times\) 4 + 26 \(\times\) 5
= 76 + 130
= 206
c, \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{3}\) - \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{4}\)
= \(\dfrac{2}{5}\) + \(\dfrac{4}{15}\) - \(\dfrac{1}{5}\)
= \(\dfrac{6}{15}\) + \(\dfrac{4}{15}\) - \(\dfrac{3}{15}\)
= \(\dfrac{7}{15}\)
d, 1\(\dfrac{5}{7}\) + 7\(\dfrac{3}{6}\) + 2\(\dfrac{2}{7}\) - 4\(\dfrac{3}{6}\)
= (1 + 2 + \(\dfrac{5}{7}\) + \(\dfrac{2}{7}\)) + ( 7 + \(\dfrac{3}{6}\) - 4 - \(\dfrac{3}{6}\))
= 3 + 1 + 3
= 7
\(\left(x+\frac{3}{4}\right)\times\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}\div\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
a, 7\(\dfrac{3}{5}\) : \(x\) = 5\(\dfrac{4}{15}\) - 1\(\dfrac{1}{6}\)
\(\dfrac{38}{5}\) : \(x\) = \(\dfrac{79}{15}\) - \(\dfrac{7}{6}\)
\(x\) = \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{38}{5}\) : \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{76}{41}\)
b, \(x\) \(\times\) 2\(\dfrac{2}{3}\) = 3\(\dfrac{4}{8}\) + 6\(\dfrac{5}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{7}{2}\) + \(\dfrac{77}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\): \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{119}{32}\)
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
X x 3 1/3= 3 1/3 : 4 1/4
X x 10/3=10/3:17/4
X x 10/3= 10/3:17/4
X x 10/3= 40/51
X = 40/51:10/3
X = 120/510
X = 12/51
X = 4/17
\(A=\dfrac{2}{1x3}+\dfrac{2}{3x5}+\dfrac{2}{5x7}+...+\dfrac{2}{21x23}\)
\(A=2x\left(\dfrac{1}{1x3}+\dfrac{1}{3x5}+\dfrac{1}{5x7}+...+\dfrac{1}{21x23}\right)\)
\(A=2x\dfrac{1}{2}x\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{21}-\dfrac{1}{23}\right)\)
\(A=1-\dfrac{1}{23}\)
\(A=\dfrac{22}{23}\)
\(B=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\)
\(B=\dfrac{1}{2x3}+\dfrac{1}{3x4}+\dfrac{1}{4x5}+\dfrac{1}{5x6}+\dfrac{1}{6x7}+\dfrac{1}{7x8}+\dfrac{1}{8x9}+\dfrac{1}{9x10}\)
\(B=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\)
\(B=\dfrac{1}{2}-\dfrac{1}{10}\)
\(B=\dfrac{5}{10}-\dfrac{1}{10}\)
\(B=\dfrac{4}{10}\)
\(B=\dfrac{2}{5}\)
\(\dfrac{3}{5}\times\dfrac{4}{7}\times1\dfrac{1}{2}\)
\(=\dfrac{3}{5}\times\dfrac{4}{7}\times\dfrac{3}{2}\)
\(=\dfrac{3\times4\times3}{5\times7\times2}\)
\(=\dfrac{3\times2\times3}{5\times7}\)
\(=\dfrac{18}{35}\)
5/4-yx5/6=-1/12
5/4-y = -1/12:5/6
5/4-y = -1/10
y = 5/4-(-1/10)
y = 27/20
\(\frac{5}{4}-y.\frac{5}{6}=\frac{1}{4}-\frac{1}{3}\)
\(\Rightarrow\frac{5}{4}-y.\frac{5}{6}=-\frac{1}{12}\)
\(\Rightarrow y.\frac{5}{6}=\frac{5}{4}-\left(-\frac{1}{12}\right)\)
\(\Rightarrow y.\frac{5}{6}=\frac{5}{4}+\frac{1}{12}\)
\(\Rightarrow y.\frac{5}{6}=\frac{4}{3}\)
\(\Rightarrow y=\frac{4}{3}:\frac{5}{6}\)
\(\Rightarrow y=\frac{8}{5}\)
Vậy \(y=\frac{8}{5}.\)
\(\left(\dfrac{1}{4}+35\%+0,65+75\%\right)\times\left(1\dfrac{6}{9}+4\dfrac{8}{24}\right)\)
\(=\left(0,25+0,35+0,65+0,75\right)\times\left(1+\dfrac{2}{3}+4+\dfrac{1}{3}\right)\)
\(=2\times6\)
\(=12\)
\(\left(\dfrac{1}{4}+35\%+0,65+75\%\right)\times\left(1\dfrac{6}{9}+4\dfrac{8}{24}\right)\)
\(=\left(\dfrac{1}{4}+\dfrac{7}{20}+\dfrac{65}{100}+\dfrac{3}{4}\right)\times\left(\dfrac{15}{9}+\dfrac{13}{3}\right)\)
\(=\left(\dfrac{5}{20}+\dfrac{7}{20}+\dfrac{13}{20}+\dfrac{15}{20}\right)\times6\)
\(=\left[\left(\dfrac{15}{20}+\dfrac{5}{20}\right)+\left(\dfrac{7}{20}+\dfrac{13}{20}\right)\right]\times6\)
\(=2\times6\)
\(=12\)
\(\frac{3}{4}+\frac{1}{3}\times a=\frac{7}{6}\)
\(\Leftrightarrow\frac{1}{3}\times a=\frac{7}{6}-\frac{3}{4}=\frac{5}{12}\)
\(\Leftrightarrow a=\frac{5}{12}\div\frac{1}{3}=\frac{5}{4}\).
\(a-\frac{1}{4}=\frac{5}{4}-\frac{1}{4}=1\)