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a: \(x+\dfrac{3}{9}=\dfrac{7}{6}\cdot\dfrac{2}{3}\)
=>\(x+\dfrac{1}{3}=\dfrac{14}{18}=\dfrac{7}{9}\)
=>\(x=\dfrac{7}{9}-\dfrac{1}{3}=\dfrac{7}{9}-\dfrac{3}{9}=\dfrac{4}{9}\)
b: \(x-\dfrac{2}{3}=\dfrac{1}{8}:\dfrac{5}{4}\)
=>\(x-\dfrac{2}{3}=\dfrac{1}{8}\cdot\dfrac{4}{5}=\dfrac{1}{10}\)
=>\(x=\dfrac{1}{10}+\dfrac{2}{3}=\dfrac{3+20}{30}=\dfrac{23}{30}\)
\(x\) \(\times\) 3 + 8 = 20
\(x\) \(\times\) 3 = 20 - 8
\(x\) \(\times\) 3 = 12
\(x\) = 12: 3
\(x\) = 4
Cậu có thể vào đây và tham khảo
Thay số để làm nhé
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Câu hỏi của nguyen toan thang - Toán lớp 6 - Học toán với OnlineMath
\(\frac{2}{5}\times\frac{1}{2}-\frac{2}{5}\times\frac{1}{3}-\frac{2}{5}\times\)\(\frac{1}{6}\)
\(=\frac{2}{5}\times\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
\(=\frac{2}{5}\times\frac{0}{6}\)
\(=\frac{2}{5}\times0\)
\(=0\)
\(\frac{2}{5}\times\frac{1}{2}-\frac{2}{5}\times\frac{1}{3}-\frac{2}{5}\times\frac{1}{6}\)
\(=\frac{2}{5}\times\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
\(=\frac{2}{5}\times0\)
\(=0\)
\(25.24+25.48+75.16+75.56\)
\(=25.\left(24+48\right)+75.\left(16+56\right)\)
\(=25.72+75.72\)
\(=\left(25+75\right).72\)
\(=100.72\)
\(=7200\)
\(A=\left(1-\dfrac{1}{4}\right)\left(1-\dfrac{1}{9}\right)\cdot...\cdot\left(1-\dfrac{1}{9801}\right)\)
\(=\left(1-\dfrac{1}{2}\right)\left(1+\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1+\dfrac{1}{3}\right)\cdot...\left(1-\dfrac{1}{99}\right)\left(1+\dfrac{1}{99}\right)\)
\(=\left(\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{98}{99}\right)\cdot\left(\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot...\cdot\dfrac{100}{99}\right)\)
\(=\dfrac{1}{99}\cdot\dfrac{100}{2}=\dfrac{50}{99}\)
\(=\dfrac{20}{21}x\dfrac{21}{22}x\dfrac{22}{23}x...x\dfrac{1999}{2000}\)
\(=\dfrac{20}{2000}=\dfrac{1}{100}\)
=20/21x21/22x22/23x..............x1998/1999x1999/2000
=20x21x22x23x.....................x1998x1999/21x22x23x24x...............x1999x2000
=20/2000
1/100
0,25 x 3 + 1 : 4 x 7
= 0,25 (3+7)
= 0,25 x 10
= 2,5
X x 1.2 + X x 1.8 = 45
X [1(2+8)] = 45
X [1 x 10] = 45
X x 10 = 45
X = 45 : 10
X = 4,5
\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+222\right)=27195\)
\(\Leftrightarrow\left(x+x+x+...+x\right)+\left(1+2+3+...+222\right)=27195\)
\(\Leftrightarrow\left(x+x+x+...+x\right)+\frac{\left(222+1\right)\left[\left(222-1\right):1+1\right]}{2}=27195\)
\(\Leftrightarrow222x+24753=27195\)
\(\Leftrightarrow222x=2442\Leftrightarrow x=11\)
\(222x+\left(1+2+3+4+...+222\right)=27195\)
1 + 2 + 3 + 4 + ... + 222
Số số hạng : ( 222 - 1 ) : 1 + 1 = 222
Tổng : ( 222 + 1 ) x 222 : 2 = 24753
\(222x+24753=27195\)
\(222x=27195-24753\)
\(222x=2442\)
\(x=11\)