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\(\frac{2}{5}\cdot\frac{1}{2}-\frac{2}{5}\cdot\frac{1}{3}-\frac{2}{5}\cdot\frac{1}{6}\)
\(=\frac{2}{5}\cdot\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
\(=\frac{2}{5}\cdot\frac{0}{6}=\frac{2}{5}\cdot0=0\)
tìm x
a) \(0,5+\left(x-\frac{15}{2}\right):\frac{1}{2}=\frac{9}{2}\)
\(\Rightarrow x=\frac{19}{2}=8,5\)
b) \(2012\cdot x-2010\cdot x=2014\)
\(\Leftrightarrow\left(2012-1010\right)\cdot x=2014\)
\(\Leftrightarrow2x=2014\)
\(\Rightarrow x=\frac{2014}{2}=1007\)
hok tốt .
Tính nhanh:
2/5 x 1/2 - 2/5 x 1/3 - 2/5 x 1/6
= 2/5 x ( 1/2 - 1/3 - 1/6 )
= 2/5 x ( 3/6 - 2/6 - 1/6 )
= 2/5 x 0/6
=0
1) 2,75 - 5/6 × 2/5 = 2,75 - (5/6) × (2/5) = 2,75 - 1/3 = 2,75 - 0,33 = 2,42
2) 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 3/4) - 3/5 = 1,25 - (5/6 - 9/12) - 3/5 = 1,25 - (10/12 - 9/12) - 3/5 = 1,25 - 1/12 - 3/5 = 1,25 - 0,08 - 0,6 = 1,25 - 0,68 = 0,57
3) 4/9 × 0,75 + 8/5 + 3,125 = (4/9) × 0,75 + 8/5 + 3,125 = 0,44 + 8/5 + 3,125 = 0,44 + 1,6 + 3,125 = 0,44 + 4,725 = 5,165
4) 1,125 - 4/7 - 0,12 = 1,125 - (4/7) - 0,12 = 1,125 - 0,57 - 0,12 = 0,435 - 0,12 = 0,315
5) (1/3 + 0,4) × 3,5 + (1/6 + 0,75) × 6/5
\(x\): 0,5 + \(x\): \(\frac{1}{3}\)+ \(x\): 0,1 - \(x\)x 5 = 1000
\(x\)x 2 + \(x\)x 3 + \(x\)x 10 - \(x\)x 5 = 1000
\(x\)x (2 + 3 + 10 - 5) = 1000
\(x\)x 10 = 1000
\(x\)= 1000 : 10
\(x\)= 100
\(x:0,5+x\) . \(\dfrac{1}{5}=1\dfrac{3}{5}\)
\(x :\)\(\dfrac{1}{2}+x.\dfrac{1}{5}=\dfrac{8}{5}\)
\(x . 2+x.\)\(\dfrac{1}{5}=\dfrac{8}{5}\)
\(x\)\((\)\(2+\)\(\dfrac{1}{5}\)\()\) \(=\)\(\dfrac{8}{5}\)
\(x.\)\(\dfrac{11}{5}=\dfrac{8}{5}\)
\(x=\)\(\dfrac{8}{5}:\dfrac{11}{5}\)
\(x=\)\(\dfrac{8}{11}\)
vậy \(x=\)\(\dfrac{8}{11}\)
\(=>x\times\left(2+\dfrac{1}{5}\right)=\dfrac{5}{3}\)
=>\(x\times\dfrac{11}{5}=\dfrac{5}{3}\)
\(x=\dfrac{5}{3}:\dfrac{11}{5}=\dfrac{25}{33}\)