\(a,\dfrac{5}{2}\times\dfrac{1}{3}+\dfrac{1}{4}=\dfrac{5}{6}+\dfrac{1}{4}=\dfrac{20}{24}+\dfrac{6}{24}=\dfrac{26}{24}=\dfrac{13}{12}\)
\(b,\dfrac{1}{2}+\dfrac{1}{3}:\dfrac{2}{5}=\dfrac{1}{2}+\dfrac{1}{3}\times\dfrac{5}{2}=\dfrac{1}{2}+\dfrac{5}{6}=\dfrac{3}{6}+\dfrac{5}{6}=\dfrac{8}{6}=\dfrac{4}{3}\)
\(c,\dfrac{4}{7}:4-\dfrac{1}{21}=\dfrac{4}{7}\times\dfrac{1}{4}-\dfrac{1}{21}=\dfrac{1}{7}-\dfrac{1}{21}=\dfrac{3}{21}-\dfrac{1}{21}=\dfrac{2}{21}\)
a) \(\dfrac{5}{2}\times\dfrac{1}{3}+\dfrac{1}{4}=\dfrac{5}{6}+\dfrac{1}{4}=\dfrac{10}{12}+\dfrac{3}{12}=\dfrac{13}{12}\)
b) \(\dfrac{1}{2}+\dfrac{1}{3}:\dfrac{2}{5}=\dfrac{1}{2}+\dfrac{1}{3}\times\dfrac{5}{2}=\dfrac{1}{2}+\dfrac{5}{6}=\dfrac{3}{5}+\dfrac{5}{6}=\dfrac{8}{6}=\dfrac{4}{3}\)
c) \(\dfrac{4}{7}:4-\dfrac{1}{21}=\dfrac{4}{7}:\dfrac{4}{1}-\dfrac{1}{21}=\dfrac{4}{7}\times\dfrac{1}{4}-\dfrac{1}{21}=\dfrac{4}{28}-\dfrac{1}{21}=\dfrac{1}{7}-\dfrac{1}{21}=\dfrac{3}{21}-\dfrac{1}{21}=\dfrac{2}{21}\)
a) đề bài
= 5/6 + 1/4
= 10/12 + 3/12
= 13/12
b) đề bài
= 1/2 + 1/3 x 5/2
= 1/2 + 5/6
= 6/12 + 10/12
= 4/3
c) đề bài
= 4/7 x 1/4 - 1/21
= 1/7 - 1/21
= 3/21 - 1/21
= 2/21
