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25 tháng 6 2017

Ta có : \(\frac{1}{4}+\frac{1}{3}:\frac{1}{x}=\frac{11}{12}\)

\(\Rightarrow\frac{1}{3}:\frac{1}{x}=\frac{11}{12}-\frac{1}{4}\)

\(\frac{1}{3}:\frac{1}{x}=\frac{2}{3}\)

\(\frac{1}{x}=\frac{1}{3}:\frac{2}{3}\)

\(\frac{1}{x}=\frac{1}{3}\times\frac{3}{2}\)

\(\frac{1}{x}=\frac{1}{2}\)

=> x = 2

25 tháng 6 2017

a) \(\frac{x\div3-16}{2}+21=38\)

\(\frac{x\div3-16}{2}=38+21\)

\(\frac{x\div3-16}{2}=59\)

\(x\div3-16=59.2\)

\(x\div3-16=118\)

\(x\div3=118+16\)

\(x\div3=134\)

\(x=134.3\)

\(x=402\)

b) \(\frac{1}{4}+\frac{1}{3}\div\frac{1}{x}=\frac{11}{12}\)

\(\frac{1}{3}\div\frac{1}{x}=\frac{11}{12}-\frac{1}{4}\)

\(\frac{1}{3}\div\frac{1}{x}=\frac{2}{3}\)

\(\frac{1}{x}=\frac{1}{3}\div\frac{2}{3}\)

\(\frac{1}{x}=\frac{1}{2}\)

Vậy x = ....

3 tháng 7 2018

Câu b:

\(\frac{21}{8}:\frac{5}{6}+\frac{1}{2}:\frac{5}{6}\)

\(\frac{63}{20}+\frac{3}{5}\)

\(\frac{15}{4}\)

7 tháng 7 2018

\(\left(\frac{21}{8}+\frac{1}{2}\right):\frac{5}{6}\)

\(\frac{25}{8}:\frac{5}{6}\)

\(\frac{25}{8}.\frac{6}{5}\)

\(\frac{30}{8}\)

6 tháng 8 2015

x-(20/11*13+20/13*15+20/15*17+...+20/553*55)=3/7

14 tháng 8 2015

(a-b)(a-b)+(b-c)(b-c)+(c-a)(c-a)=(a+b-2c)(a+b-2c)+(b+c-2a)(b+c-2a)+(c+a-2b)(c+a-2b)

Cm:a=b=c

24 tháng 10 2017

a, 7/5 : x + 3/2 = 16/3

7/5 : x = 16/3 - 3/2

7/5 : x = 23/6

x = 7/5 : 23/6

x = 42/115

b, x : 1/5 + 1/7 = 3/5 . 18/21

x : 1/5 + 1/7 = 18/35

x : 1/5 = 18/35 - 1/7

x : 1/5 = 13/35

x = 13/35 . 1/5

x = 13/175

c, x - 1 và 1/3 : 2 = 5/7

x - 4/3 : 2 = 5/7

x - 4/3 = 5/7 . 2

x - 4/3 = 10/7

x = 10/7 + 4/3

x = 58/21

d, x + 2 và 3/5 . 1/6 = 35/36

x + 13/5 . 1/6 = 35/36

x + 13/5 = 35/36 : 1/6

x + 13/5 = 35/6

x = 35/6 - 13/5

x = 97/30

e, ( x + 3/2 ) : 2 = 7/10 + 1/5

( x + 3/2 ) : 2 = 9/10

x + 3/2 = 9/10 . 2

x + 3/2 = 9/5

x = 9/5 - 3/2

x = 3/10

26 tháng 7 2018

\(\frac{11}{9}+\frac{35}{18}\)

\(=\frac{19}{6}\)

\(\frac{22}{21}:\frac{1}{2}+\frac{25}{12}:\frac{1}{2}\)

\(\frac{44}{21}+\frac{25}{6}\)

\(\frac{263}{42}\)

13 tháng 7 2018

a) (1,5 . 1,9 - x - 0,5) : 0,25 = 7,5 : 0,125

=> (2,85 - x - 0,5) : 0,25 = 60

=> (2,85 - 0,5) - x = 60 . 0,25

=> 2,35 - x = 15

=> x = 2,35 - 15

=> x = -12,65

Vậy x = -12,65

b) \(1-\left(5\frac{2}{9}+x-7\frac{7}{18}\right)\div2\frac{1}{6}=0\)

\(\Rightarrow\left(5\frac{2}{9}-7\frac{7}{18}+x\right)\div2\frac{1}{6}=1-0\)

\(\Rightarrow\left(\frac{47}{9}-\frac{133}{18}+x\right)\div2\frac{1}{6}=1\)

\(\Rightarrow\frac{-13}{6}+x=2\frac{1}{6}\)

\(\Rightarrow x=2\frac{1}{6}-\frac{-13}{6}\)

\(\Rightarrow x=\frac{13}{6}+\frac{13}{6}\)

\(\Rightarrow x=\frac{26}{6}\)

\(\Rightarrow x=\frac{13}{3}\)

Vậy \(x=\frac{13}{3}\)

c) \(35\left(2\frac{1}{5}-x\right)=32\)

\(\Rightarrow2\frac{1}{5}-x=32\div35\)

\(\Rightarrow\frac{11}{5}-x=\frac{32}{35}\)

\(\Rightarrow x=\frac{11}{5}-\frac{32}{35}\)

\(\Rightarrow x=\frac{9}{7}\)

Vậy \(x=\frac{9}{7}\)

d) \(\frac{4}{3}+\left(x\div2\frac{2}{3}-0,5\right).1\frac{35}{55}=0,6\)

\(\Rightarrow\left(x\div\frac{8}{3}-\frac{1}{2}\right).\frac{18}{11}=\frac{3}{5}-\frac{4}{3}\)

\(\Rightarrow\left(x\div\frac{8}{3}-\frac{1}{2}\right).\frac{18}{11}=\frac{-11}{15}\)

\(\Rightarrow x\div\frac{8}{3}-\frac{1}{2}=\frac{-11}{15}\div\frac{18}{11}\)

\(\Rightarrow x\div\frac{8}{3}-\frac{1}{2}=\frac{-121}{270}\)

\(\Rightarrow x\div\frac{8}{3}=\frac{-121}{270}+\frac{1}{2}\)

\(\Rightarrow x\div\frac{8}{3}=\frac{7}{135}\)

\(\Rightarrow x=\frac{7}{135}.\frac{8}{3}\)

\(\Rightarrow x=\frac{56}{405}\)

Vậy \(x=\frac{56}{405}\)

e) \(1\frac{1}{3}.2\frac{2}{4}\div\frac{5}{6}.1\frac{1}{11}=11-5\div x\)

\(\Rightarrow\frac{4}{3}.\frac{5}{2}\div\frac{5}{6}.\frac{12}{11}=11-5\div x\)

\(\Rightarrow\frac{10}{3}\div\frac{5}{6}.\frac{12}{11}=11-5\div x\)

\(\Rightarrow4.\frac{12}{11}=11-5\div x\)

\(\Rightarrow11-5\div x=\frac{48}{11}\)

\(\Rightarrow5\div x=11-\frac{48}{11}\)

\(\Rightarrow5\div x=\frac{73}{11}\)

\(\Rightarrow x=5\div\frac{73}{11}\)

\(\Rightarrow x=\frac{55}{73}\)

Vậy \(x=\frac{55}{73}\)

a) (1,5 * 1,9 - x - 0,5) : 0,25 = 7,5 : 0,125

(2,85 - x - 0,5) : 0,25 = 60

(2,85 - x - 0,5) = 60 x 0,25

(2,85 - x - 0,5) = 15

2,35 - x = 15

x = 2,35 - 15

x = -12,65

3 tháng 6 2019

Bài 2:

\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).......\left(1-\frac{1}{2004}\right)\)

\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}....\frac{2003}{2004}\)

\(=\frac{1}{2004}\)

3 tháng 6 2019

Bài 2

=1/2 x 2/3 ... x 2003/2004

=1/2004

8 tháng 8 2015

a, (x+2)+(x+4)+(x+6)+...+(x+100)=6000

(x+x+x+...+x)+(2+4+6+...+100)=6000

50.x+2550=6000

50.x=6000-2550

50.x=3450

x=3450:50

x=69

b, 1+2+3+4+...+x=15

10+...+x=15

x=15-10

x=5

Nho **** cho minh nha

 

26 tháng 2 2016

Ta có: (x+x+x+...+x) + (2+4+6+...+100) = 6000

Ta thấy vế phải có: (100-2):2+1=50(số hạng)

Tổng của vế phải: [(2+100)*50]:2=2550

\(\Rightarrow\)có 50 số x

\(\Rightarrow\)50*x + 2550 = 6000

\(\Rightarrow\)50*x=6000-2550

\(\Rightarrow\)50*x=3450

\(\Rightarrow\)x=3450:50

\(\Rightarrow\)x=69

   Vậy x=69

Mình đúng nè, nhớ k nha

13 tháng 6 2017

a,

\(x+\frac{7}{15}=1\frac{1}{20}\)

\(x+\frac{7}{15}=\frac{21}{20}\)

\(x=\frac{21}{20}-\frac{7}{15}=\frac{63}{60}-\frac{28}{60}\)

\(x=\frac{35}{60}=\frac{7}{12}\)

b, 

\(\left[3\frac{1}{2}-x\right]\cdot1\frac{1}{4}=\frac{15}{16}\)

\(\left[\frac{7}{2}-x\right]\cdot\frac{5}{4}=\frac{15}{16}\)

\(\frac{7}{2}-x=\frac{15}{16}:\frac{5}{4}=\frac{3}{4}\)

\(\frac{7}{2}-x=\frac{3}{4}\Rightarrow x=\frac{7}{2}-\frac{3}{4}\)

\(x=\frac{11}{4}\)

c, 

\(1\frac{1}{5}x+\frac{2}{3}x=\frac{56}{125}\Leftrightarrow\frac{6}{5}x+\frac{2}{3}x=\frac{56}{125}\)

\(\frac{28}{15}x=\frac{56}{125}\Rightarrow x=\frac{6}{25}\)

d,

\(60\%x+0,4x+x:3=2\)

\(\frac{3}{5}x+\frac{2}{5}x+\frac{1}{3}x=2\)

\(\frac{4}{3}x=2\Rightarrow x=\frac{3}{2}\)

 Nguyễn Anh Thiện 

a) 

x + \(\frac{7}{15}\)  = \(1\frac{1}{20}\)  

X + \(\frac{7}{15}=\frac{21}{20}\)   

X            \(=\frac{21}{20}-\frac{7}{15}\)  

X             \(=\frac{63}{60}-\frac{28}{60}=\frac{35}{60}=\frac{7}{12}\)     

^^ Học tốt !