Question

tính giá trị biểu thức: 2/3 x (1/2 + 1/3)=______________  5/7 - 2/5 : 11/7=_________________

Answer 1

\(\dfrac{2}{3}\times\left(\dfrac{1}{2}+\dfrac{1}{3}\right)\)
\(=\dfrac{2}{3}\times\left(\dfrac{3}{6}+\dfrac{2}{6}\right)\)
\(=\dfrac{2}{3}\times\dfrac{5}{6}\)
\(=\dfrac{1\times5}{3\times3}\)
\(=\dfrac{5}{9}\)

\(\dfrac{5}{7}-\dfrac{2}{5}:\dfrac{11}{7}\)
\(=\dfrac{5}{7}-\dfrac{2}{5}.\dfrac{7}{11}\)
\(=\dfrac{5}{7}-\dfrac{14}{55}\)
\(=\dfrac{275}{385}-\dfrac{98}{385}\)
\(=\dfrac{275-98}{385}\)
\(=\dfrac{177}{385}\)