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Bài 1:
$(y+\frac{1}{3})+(y+\frac{1}{9})+(y+\frac{1}{27})+(y+\frac{1}{81})=\frac{56}{81}$
$(y+y+y+y)+(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81})=\frac{56}{81}$
$4\times y+\frac{40}{81}=\frac{56}{81}$
$4\times y=\frac{56}{81}-\frac{40}{81}=\frac{16}{81}$
$y=\frac{16}{81}:4=\frac{4}{81}$
Bài 2:
$18: \frac{x\times 0,4+0,32}{x}+5=14$
$18: \frac{x\times 0,4+0,32}{x}=14-5=9$
$\frac{x\times 0,4+0,32}{x}=18:9=2$
$x\times 0,4+0,32=2\times x$
$2\times x-x\times 0,4=0,32$
$x\times (2-0,4)=0,32$
$x\times 1,6=0,32$
$x=0,32:1,6=0,2$
\(x+1+\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}=2\)
\(\Leftrightarrow x+\dfrac{121}{81}=2\)
hay \(x=\dfrac{41}{81}\)
Tham khảo link: https://olm.vn/hoi-dap/detail/55111422944.html
`(x+1/3)+(x+1/9)+(x+1/27)+(x+1/81)=56/81`
`x+x+x+x+1/3+1/9+1/27=56/81-1/81`
`4x+13/27=55/81`
`4x=55/81-13/27`
`4x=55/81-52/81`
`4x=16/81`
`x=4/108`
Vậy `x=4/108`
a: =13/26*9/18*2/3=2/3*1/4=2/12=1/6
b: =44/22*5/15*3/2=2*1/3*3/2=2*1/2=1
`3+4/9xx7/25xx27/12xx3 4/7-7/25`
`=3+4/9xx7/25xx27/12xx25/7-7/25`
`=3+7/25xx25/7xx4/9xx27/12-7/25`
`=3+4/9xx9/4xx1-7/25`
`=3+1xx1-7/25`
`=3+1-7/25`
`=75/25+25/25-7/25`
`=93/25`
\(M=3+\dfrac{4}{9}\times\dfrac{7}{25}\times\dfrac{27}{12}\times3\dfrac{4}{7}-\dfrac{7}{25}\)
\(=3+\dfrac{4}{9}\times\dfrac{7}{25}\times\dfrac{27}{12}\times\dfrac{25}{7}-\dfrac{7}{25}\)
\(=3+\left(\dfrac{4}{9}\times\dfrac{27}{12}\right)\times\left(\dfrac{7}{25}\times\dfrac{25}{7}\right)-\dfrac{7}{25}\)
\(=3+\left(\dfrac{4\times3\times9}{9\times3\times4}\right)\times1-\dfrac{7}{25}\)
\(=3+1\times1-\dfrac{7}{25}\)
\(=3+1-\dfrac{7}{25}\)
\(=4-\dfrac{7}{25}\)
\(=\dfrac{100}{25}-\dfrac{7}{25}\)
\(=\dfrac{93}{25}\)
\(\left(1\dfrac{2}{9}+\dfrac{11}{6}\right)\times\dfrac{27}{11}-0,5=\left(\dfrac{11}{9}+\dfrac{11}{6}\right)\times\dfrac{27}{11}-\dfrac{1}{2}=\left(\dfrac{66+99}{54}\right)\times\dfrac{27}{11}-\dfrac{1}{2}=\dfrac{165}{54}\times\dfrac{27}{11}-\dfrac{1}{2}=\dfrac{135}{8}-\dfrac{1}{2}=\dfrac{135}{8}-\dfrac{4}{8}=\dfrac{131}{8}\)
1.
x : \(\dfrac{2}{9}=18\)
x = 18 x \(\dfrac{2}{9}\)
x = 4
\(\Rightarrow\) Chọn C
2.
\(\dfrac{3}{5}\) của 4 tấn:
Đổi: 4 tấn = 4000 kg.
\(\dfrac{3}{5}\) của 4000 kg là:
4000 x \(\dfrac{3}{5}\) = 2400 kg
\(\Rightarrow\) Chọn A
3. 25ha = ... km2
Ta có: 1ha = 0,01 km2
\(\Rightarrow\) 25ha = 0,01 x 25 = 0,25 km2
\(\Rightarrow\) Chọn C
`( x + 18 )/9 = x/27`
`=> ( 3x + 54 )/27 = x/27`
`=> 3x+54=x`
`=> 3x-x=-54`
`=> 2x=-54`
`=>x=-27`
Vậy `x=-27`
thanh kiu ve ri mắch