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\(\frac{3}{4}+6,8+0,25+0,5+\frac{1}{5}+\frac{1}{2}\)
\(=0,75+6,8+0,25+0,5+0,2+0,5\)
\(=\left(0,75+0,25\right)+\left(6,8+0,2\right)+\left(0,5+0,5\right)\)
\(=1+7+1\)
\(=9\)
\(=\frac{120-0,5\cdot40\cdot5\cdot0,2\cdot20\cdot0,25-20}{1+5+9+.....+33+37}\)
\(=\frac{120-20-\left(0,5\cdot20\right)\cdot\left(5\cdot0,2\right)\cdot\left(40\cdot0,25\right)}{1+5+9+.....+33+37}\)
\(=\frac{100-10\cdot1\cdot10}{1+5+9+.....+33+37}\)
\(=\frac{100-100}{1+5+9+.....+33+37}\)
\(=\frac{0}{1+5+9+.....+33+37}\)
\(=0\)
Ta có:\(120-0,5\times40\times5\times0,2\times20\times0,25-20=120-100-20=0\)
\(\Rightarrow\frac{120-0,5\times40\times5\times0,2\times20\times0,25}{1+5+.......+37}=\frac{0}{1+5+9+.....+37}=0\)
Vậy...........
đề = \(\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{50.51}\)( áp dụng c.thức tính tổng )
= ..........
= 2 .( \(\frac{1}{2}-\frac{1}{51}\))
= dễ
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
2 x 3 x 4 x 8 + 0.5 x 0.25 x 0.25
= 6 x 4 x 8 + 0.5 x 0.25 x 0.25
= 24 x 8 + 0.125 x 0.25
= 192 + 0.0625
= 192.0625
1/2 : 0,5 - 1/4 : 0,25 - 1/8 - 0,125 : 1/10 - 0,1 = 1/2 : 1/2 - 1/4 : 1/4 - 1/8 - 1/8 : 1/10 - 1/10 .
= 1 - 1 - 1/8 - 1/10 : ( 1/8 - 1 ) .
= 0 - 1/8 - 1/10 : ( -7/8 ) .
= -7/8 - 1/10 : ( -7/8 ) .
= -7/8 : ( 1 - 1/10 ) .
= -7/8 : 9/10 .
= -7/8 . 10/9 .
= -35/36 .
\(\left(6\dfrac{2}{5}+0,5\right):\dfrac{1}{4}+\dfrac{2}{5}\)
\(=\left(\dfrac{32}{5}+\dfrac{1}{2}\right):\dfrac{1}{4}+\dfrac{2}{5}\)
\(=\left(\dfrac{64}{10}+\dfrac{5}{10}\right)\times4+\dfrac{2}{5}\)
\(=\dfrac{69}{10}\times4+\dfrac{2}{5}\)
\(=\dfrac{276}{10}+\dfrac{2}{5}=\dfrac{138}{5}+\dfrac{2}{5}\)
\(=\dfrac{140}{5}=28\)
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\(32\times\dfrac{4}{5}+6,8\)
\(=32\times\dfrac{4}{5}+\dfrac{34}{5}\)
\(=\dfrac{128}{5}+\dfrac{34}{5}\)
\(=\dfrac{162}{5}\)
\(\frac{3}{4}+6,8+0,25+0,5+\frac{1}{2}+\frac{1}{5}=\left(\frac{3}{4}+0,25\right)+\left(6,8+\frac{1}{5}\right)+\left(0,5+\frac{1}{2}\right)\)
\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{34}{5}+\frac{1}{5}\right)+\left(\frac{1}{2}+\frac{1}{2}\right)\)
\(=1+7+1=9\)
3/4 + 6,8 + 0,25 + 0,5 + 1/2 + 1/5
= 9
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