Ta có :C = 2181 - 729 + 243 . 81 - 27

= 2052 + 19683 - 27

C = 21108

D = 3² . 9² . 243 + 18 . 243 . 324 + 723 . 729

=9 . 81 . 243 + 18 . 243 . 324 . 243

= 177147 + 344373768

=  344550915

Ta có : C : D = 21108 : 344550915 = 0,00006

\((\dfrac{-5}{18}).\dfrac{-9}{10}=\dfrac{-50}{180}.\dfrac{-162}{180}=\dfrac{8100}{180}=45\) 

\((\dfrac{-1}{4})^2.\dfrac{4}{11}+\dfrac{7}{11}.(\dfrac{-1}{4}^2)=(\dfrac{-1}{16}).\dfrac{4}{11}+\dfrac{7}{11}.(\dfrac{-1}{16})=(\dfrac{-1}{16}).(\dfrac{4}{11}+\dfrac{7}{11})=(\dfrac{-1}{16}).1=\dfrac{-1}{16}\)

Số tiền bác Lan đi mua gạo là :

      90000 x 3 : 5 = 54000 ( đồng )

  Số tiền bác Lan đi mua thịt là :

      54000 x 2 : 3 = 36000 ( đồng )

Bác Lan còn lại số tiền là :

90000 - 36000 - 54000 = 0 ( đồng )

a)= \(\dfrac{120.120.120}{40.40.40}=\dfrac{1728000}{64000} = 27\)

\((\dfrac{55}{49}:\dfrac{5}{9}). \dfrac{7}{33}= (\dfrac{55}{49}.\dfrac{9}{5}).\dfrac{7}{33}= \dfrac{495}{225}.\dfrac{7}{33} = \dfrac{3465}{7425}\)

nhầm dấu thui mà

\(\dfrac{22}{5}:22=\dfrac{2}{5}.\dfrac{22}{1}= \dfrac{22}{5} .\dfrac{1}{22}=\dfrac{22}{110}\)

a) = (\(\dfrac{22}{5}+\dfrac{17}{7})-(\dfrac{12}{5}-\dfrac{39}{7})\) 

= \((\dfrac{22}{5}+\dfrac{12}{5})-(\dfrac{17}{7}-\dfrac{39}{7})\)

= \(\dfrac{34}{5}+\dfrac{22}{7}\)

= \(\dfrac{238}{35}+\dfrac{110}{35}=\dfrac{348}{35}\)

b= \((\dfrac{43}{4}+\dfrac{19}{5})-(\dfrac{23}{4}-\dfrac{6}{5})\) 

= \((\dfrac{43}{4}+\dfrac{23}{4})-(\dfrac{19}{5}-\dfrac{6}{5})\) 

= \(\dfrac{33}{2}+\dfrac{13}{5}\) 

= \(\dfrac{65}{10}+\dfrac{26}{10} = \dfrac{81}{10}\)

\(\dfrac{1}{5}\) tấn ..<.. 200 kg ;        \(\)    1 tấn 5 kg .<... 1500 kg ;              1020 kg ..=.. 1 tấn 2 kg