Bài 10:
a: \(A=\dfrac{10}{11}+\dfrac{1}{11}\cdot\dfrac{3}{11}+\dfrac{1}{11}\cdot\dfrac{8}{11}\)
\(=\dfrac{10}{11}+\dfrac{1}{11}\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\)
\(=\dfrac{10}{11}+\dfrac{1}{11}=\dfrac{11}{11}=1\)
b: \(B=\dfrac{5}{7}\cdot\dfrac{40}{11}-\dfrac{5}{11}\cdot\dfrac{117}{7}\)
\(=\dfrac{5}{7}\left(\dfrac{40}{11}-\dfrac{117}{11}\right)\)
\(=\dfrac{5}{7}\cdot\dfrac{-77}{11}=\dfrac{5}{7}\cdot\left(-7\right)=-5\)
c: \(C=\dfrac{3}{7}\cdot\dfrac{9}{11}+\dfrac{3}{7}\cdot\dfrac{5}{11}-\dfrac{3}{7}\cdot\dfrac{25}{11}\)
\(=\dfrac{3}{7}\left(\dfrac{9}{11}+\dfrac{5}{11}-\dfrac{25}{11}\right)\)
\(=\dfrac{3}{7}\cdot\dfrac{-11}{11}=-\dfrac{3}{7}\)
d: \(D=\dfrac{5}{7}\cdot\dfrac{-3}{38}\cdot\dfrac{7}{10}\cdot\dfrac{19}{6}\)
\(=\dfrac{5}{7}\cdot\dfrac{7}{10}\cdot\dfrac{-3}{6}\cdot\dfrac{19}{38}\)
\(=\dfrac{5}{10}\cdot\dfrac{-1}{2}\cdot\dfrac{1}{2}=\dfrac{-1}{8}\)
Bài 11:
a: Sau hai ngày thì lượng sữa còn lại chiếm:
\(1-\dfrac{1}{5}-\dfrac{1}{4}=1-\dfrac{9}{20}=\dfrac{11}{20}\)(hộp)
b: Lượng sữa còn lại sau 2 ngày là:
\(1000\cdot\dfrac{11}{20}=550\left(ml\right)\)
