Question

1) Thực hiện phép tính nhanh nhất nếu có thể:

a) 

\(\dfrac{2}{7}+\dfrac{7}{7}.\dfrac{14}{25}\)

b) 

\(\dfrac{6}{7}+\dfrac{5}{7}:5-\dfrac{8}{9}\)

c)

\(\left(\dfrac{-5}{28}+1,75+\dfrac{8}{35}\right):\left(-3\dfrac{9}{20}\right)\)

d)\(70,5-528:\dfrac{15}{2}\)

e)\(\dfrac{-7}{25}.\dfrac{39}{-14}.\dfrac{50}{78}\)

 

 

Answer 1

a ) 

\(\frac{2}{7}+\frac{7}{7}.\frac{14}{25}\)

\(=\frac{2}{7}+1.\frac{14}{25}=\frac{2}{7}+\frac{14}{25}\)

\(=\frac{50}{175}+\frac{98}{175}=\frac{148}{175}\)

b)

\(\frac{6}{7}+\frac{5}{7}:5-\frac{8}{9}\)

\(=\frac{6}{7}+\frac{5}{30}-\frac{8}{9}\)

\(=\frac{6}{7}+\frac{1}{6}-\frac{8}{9}\)

\(=\frac{36}{42}+\frac{7}{42}-\frac{8}{9}\)

\(=\frac{43}{42}-\frac{8}{9}=\frac{129}{126}-\frac{112}{126}=\frac{17}{126}\)

tk ủng hộ mk nha!!!!!!!!