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\(a,\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{4}{7}+\dfrac{1}{7}+\dfrac{2}{7}\right)=1+1=2\)
\(b,\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{5}{6}\right)=\dfrac{7}{3}+\dfrac{4}{3}=\dfrac{11}{3}\)
a)\(\dfrac{3}{5}+\dfrac{4}{7}+\dfrac{2}{5}+\dfrac{1}{7}+\dfrac{2}{7}\)
\(=\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{4}{7}+\dfrac{1}{7}+\dfrac{2}{7}\right)\)
\(=1+1\)
\(=2\)
b)\(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{4}{3}+\dfrac{2}{6}+\dfrac{2}{3}+\dfrac{5}{6}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{5}{6}\right)\)
\(=\dfrac{7}{3}+\dfrac{4}{3}\)
\(=\dfrac{11}{3}\)
sau 2 giờ ô tô đi đc số phần quãng đường là:
1/4+1/6=5/12(quãng đường)
đs:........
\(a,\dfrac{2}{5}+\dfrac{9}{15}=\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\\ b,\dfrac{15}{45}+\dfrac{25}{30}=\dfrac{1}{3}+\dfrac{5}{6}=\dfrac{2}{6}+\dfrac{5}{6}=\dfrac{7}{6}\\ c,\dfrac{1}{6}+\dfrac{8}{24}=\dfrac{1}{6}+\dfrac{1}{3}=\dfrac{1}{6}+\dfrac{2}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
A) \(\dfrac{2}{5}\) + \(\dfrac{9}{15}\) B) \(\dfrac{15}{45}\) + \(\dfrac{25}{30}\) C) \(\dfrac{1}{6}\) + \(\dfrac{8}{24}\)
= \(\dfrac{2}{5}\) + \(\dfrac{3}{5}\) = \(\dfrac{1}{3}\) + \(\dfrac{5}{6}\) = \(\dfrac{1}{6}\) + \(\dfrac{1}{3}\)
= \(\dfrac{5}{5}\) = 1 = \(\dfrac{2}{6}\) + \(\dfrac{5}{6}\) = \(\dfrac{1}{6}\) + \(\dfrac{2}{6}\)
= \(\dfrac{7}{6}\) = \(\dfrac{3}{6}\) = \(\dfrac{1}{2}\)
C
C