dai gia dinh online math oi, giup minh di cac ban

147/50

a) \(\left(\dfrac{1}{2}+\dfrac{1}{6}+...+\dfrac{1}{90}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{9\cdot10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow\left(1-\dfrac{1}{2}+\dfrac{1}{2}-...+\dfrac{1}{9}-\dfrac{1}{10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow\left(1-\dfrac{1}{10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow\dfrac{9}{10}\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow90-\left[\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)=90-89\)

\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{103}{50}\right)=1\)

\(\Rightarrow x+\dfrac{103}{50}=\dfrac{5}{2}\)

\(\Rightarrow x=\dfrac{11}{25}\)

b) \(x\cdot9,85+x\cdot0,15=0,1\)

\(\Rightarrow x\cdot\left(9,85+0,15\right)=0,1\)

\(\Rightarrow x\cdot10=0,1\)

\(\Rightarrow x=\dfrac{0,1}{10}\)

\(\Rightarrow x=0,01\)

c) \(\dfrac{2}{5}+2022x=\dfrac{4}{10}\)

\(\Rightarrow\dfrac{2}{5}+2022x=\dfrac{2}{5}\)

\(\Rightarrow2022x=\dfrac{2}{5}-\dfrac{2}{5}\)

\(\Rightarrow2022x=0\)

\(\Rightarrow x=\dfrac{0}{2022}\)

\(\Rightarrow x=0\)

a) \(\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{90}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\left(1\right)\)

Ta có :

\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{90}\)

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\)

\(=1-\dfrac{1}{10}=\dfrac{9}{10}\)

\(\left(1\right)\Rightarrow\dfrac{9}{10}.100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Rightarrow90-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right].2=89\)

\(\Rightarrow\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right].2=90-89\)

\(\Rightarrow\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)=\dfrac{1}{2}\)

\(\Rightarrow x+\dfrac{206}{100}=\dfrac{5}{2}:\dfrac{1}{2}\)

\(\Rightarrow x+\dfrac{103}{50}=\dfrac{5}{2}.\dfrac{2}{1}\)

\(\Rightarrow x+\dfrac{103}{50}=5\)

\(\Rightarrow x=5-\dfrac{103}{50}\)

\(\Rightarrow x=\dfrac{250}{50}-\dfrac{103}{50}\)

\(\Rightarrow x=\dfrac{147}{50}\)

(89 x 12-2 x 6 x 89) + (145 x 54 + 146 x 45+ 100)
= ( 1068 - 1068) + ( 7830 + 6570 + 100)

= 0 + 7830 + 6570 + 100

= 14400 + 100

= 14500

0+14500=14500

10+90=100

11+89=100

12+88=100

100+5+78+22+100+78+95+22=500

10+90=100

11+89=100

12+88=100

100+5+78+22+100+78+95+22=500

10 + 90 = 100

11 + 89 = 100

12 + 88 = 100

100 + 5 + 78 + 22 + 100 + 78 + 95 + 22

= 100 + 100 + ( 5 + 95 ) + ( 78 + 22 ) + ( 78 + 22 )

= 100 x 5

= 500

a, 200 - 3( x - 16 ) = 20

        3( x - 16 )     = 200 - 20 = 180

             x - 16     = 180 : 3 = 60 

                 x        = 60 + 16  =  76

b, 5 + 10 + 15 + .............. + 95 + 100 + 105 = 1200

c, x + ( 99 - 97 + 95 - 93 + ............ + 7 - 5 + 3 - 1 ) = 100

       x + ( 2 . 25 ) = 100

         x + 50       = 100

             x           = 100 - 50 = 50

****, thks 

Ta có:

+) 10/20 : 1/6% + 69%

= 10/20 x 6%/1 + 69%

= \(\frac{10}{20}\text{x}\frac{6}{100}+\frac{69}{100}\)

=\(\frac{3}{100}+\frac{69}{100}\)

=\(\frac{72}{100}\)= 0,72

+) \(\frac{20}{2}:100\%\text{x}6:100\text{x}89\%\)

=\(\frac{20}{2}\text{x}6\text{x}89\%:\left(100\%\text{x}100\right)\)

=\(\frac{20}{2}\text{x}6\text{x}\frac{89}{100}:100\)

=\(\frac{20\text{x}6\text{x}89}{2\text{x}100\text{x}100}\)

=\(\frac{3\text{x}89}{5x100}\)

=\(\frac{267}{500}\)

=0.534

ủng hộ mik nhé

\(\frac{10}{20}:\frac{1}{6}\%+69\%=300,69\)

\(\frac{20}{2}:100\%x6:100x89\%=0,534\)