Câu hỏi của Nguyễn Duy

Question

2,Thực hiện phép tính(tính nhanh nếu có thể)

a,$\frac{2}{3}+\frac{1}{3}\cdot\left(-\frac{2}{5}\right)$

b,$0,75\cdot1\frac{7}{9}-1\frac{2}{5}:\frac{-21}{20}$

c,\(\frac{-2}{17}+\frac{15}{23}+\fra...

👁💧👄💧👁 · Accepted Answer

a) $\frac{2}{3}+\frac{1}{3}\cdot\left(-\frac{2}{5}\right)\
=\frac{2}{3}+\frac{-2}{15}\
=\frac{10}{15}+\frac{-2}{15}\
=\frac{8}{15}$

b) $0,75\cdot1\frac{7}{9}-1\frac{2}{5}:\frac{-21}{20}\
=\frac{3}{4}\cdot\frac{16}{9}-\frac{7}{5}\cdot\frac{-20}{21}\
=\frac{4}{3}-\frac{-4}{3}\
=\frac{4}{3}+\frac{4}{3}\
=\frac{4}{3}\cdot2\
=\frac{8}{3}$

c) $\frac{-2}{17}+\frac{15}{23}+\frac{15}{-17}-\frac{-4}{19}+\frac{8}{23}\
=\frac{-2}{17}+\frac{15}{23}+\frac{-15}{17}+\frac{4}{19}+\frac{8}{23}\
=\left(\frac{-2}{17}+\frac{-15}{17}\right)+\left(\frac{15}{23}+\frac{8}{23}\right)+\frac{4}{19}\
=\left(-1\right)+1+\frac{4}{19}\
=0+\frac{4}{19}\
=\frac{4}{19}$

d) $2019^0\cdot\left(6-2\frac{4}{5}\right)\cdot3\frac{1}{8}-1\frac{3}{5}:25\%\
=1\cdot\left(\frac{30}{5}-\frac{14}{5}\right)\cdot\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\
=1\cdot\frac{16}{5}\cdot\frac{25}{8}-\frac{8}{5}\cdot4\
=\frac{16}{5}\cdot\frac{25}{8}-\frac{32}{5}\
=\frac{50}{5}-\frac{32}{5}\
=\frac{18}{5}$

e) $\left(\frac{7}{8}-\frac{1}{2}\right)\cdot2\frac{2}{3}-\frac{3}{7}\cdot\left(2,5^2\right)\
=\left(\frac{7}{8}-\frac{4}{8}\right)\cdot\frac{8}{3}-\frac{3}{7}\cdot6,25\
=\frac{3}{8}\cdot\frac{8}{3}-\frac{3}{7}\cdot\frac{25}{4}\
=1-\frac{75}{28}\
=\frac{28}{28}-\frac{75}{28}\
=\frac{-47}{28}$Câu trả lời: a) $\frac{2}{3}+\frac{1}{3}\cdot\left(-\frac{2}{5}\right)\
=\frac{2}{3}+\frac{-2}{15}\
=\frac{10}{15}+\frac{-2}{15}\
=\frac{8}{15}$

b) $0,75\cdot1\frac{7}{9}-1\frac{2}{5}:\frac{-21}{20}\
=\frac{3}{4}\cdot\frac{16}{9}-\frac{7}{5}\cdot\frac{-20}{21}\
=\frac{4}{3}-\frac{-4}{3}\
=\frac{4}{3}+\frac{4}{3}\
=\frac{4}{3}\cdot2\
=\frac{8}{3}$

c) $\frac{-2}{17}+\frac{15}{23}+\frac{15}{-17}-\frac{-4}{19}+\frac{8}{23}\
=\frac{-2}{17}+\frac{15}{23}+\frac{-15}{17}+\frac{4}{19}+\frac{8}{23}\
=\left(\frac{-2}{17}+\frac{-15}{17}\right)+\left(\frac{15}{23}+\frac{8}{23}\right)+\frac{4}{19}\
=\left(-1\right)+1+\frac{4}{19}\
=0+\frac{4}{19}\
=\frac{4}{19}$

d) $2019^0\cdot\left(6-2\frac{4}{5}\right)\cdot3\frac{1}{8}-1\frac{3}{5}:25\%\
=1\cdot\left(\frac{30}{5}-\frac{14}{5}\right)\cdot\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\
=1\cdot\frac{16}{5}\cdot\frac{25}{8}-\frac{8}{5}\cdot4\
=\frac{16}{5}\cdot\frac{25}{8}-\frac{32}{5}\
=\frac{50}{5}-\frac{32}{5}\
=\frac{18}{5}$

e) $\left(\frac{7}{8}-\frac{1}{2}\right)\cdot2\frac{2}{3}-\frac{3}{7}\cdot\left(2,5^2\right)\
=\left(\frac{7}{8}-\frac{4}{8}\right)\cdot\frac{8}{3}-\frac{3}{7}\cdot6,25\
=\frac{3}{8}\cdot\frac{8}{3}-\frac{3}{7}\cdot\frac{25}{4}\
=1-\frac{75}{28}\
=\frac{28}{28}-\frac{75}{28}\
=\frac{-47}{28}$

DTD2006ok · Answer

a, $\frac{2}{3}+\frac{1}{3}.\left(\frac{-2}{5}\right)$

= $\frac{2}{3}+\frac{-2}{15}=\frac{8}{15}$

b, $0,75.1\frac{7}{9}-1\frac{2}{5}:\frac{-21}{20}$

= $\frac{3}{4}.\frac{16}{9}-\frac{7}{5}.\frac{-20}{21}$

= $\frac{4}{3}-\left(\frac{-4}{3}\right)=\frac{8}{3}$

c, $\frac{-2}{17}+\frac{15}{23}+\frac{15}{-17}+\frac{4}{19}+\frac{8}{23}$

= $\left(\frac{-2}{17}+\frac{-15}{17}\right)+\left(\frac{15}{23}+\frac{8}{23}\right)+\frac{4}{19}$

= $\left(-1\right)+1+\frac{4}{19}=0+\frac{4}{19}=\frac{4}{19}$

d, $\left(6-2\frac{4}{5}\right).3\frac{1}{8}-1\frac{3}{5}:25\%$

=> $\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:25\%$

=  $\frac{16}{5}.\frac{25}{8}-\frac{8}{5}.25:100$

= 10 - 0,4 = 9,6

e, $\left(\frac{7}{8}-\frac{1}{2}\right).2\frac{2}{3}-\frac{3}{7}.\left(2,5^2\right)$

=> $\frac{3}{8}.\frac{8}{3}-\frac{3}{7}.6,25$

= $1-\frac{75}{28}=\frac{-47}{28}$Câu trả lời: a, $\frac{2}{3}+\frac{1}{3}.\left(\frac{-2}{5}\right)$