Đáp án:
1)
20% của a$=\dfrac{1}{18}$
$\dfrac{5}{8}$ của b $=\dfrac{7}{8}$
2)
$\dfrac{3}{4}$ của M $=-3$
$\dfrac{4}{3}$ của N $=\dfrac{-64}{13}$
Giải thích các bước giải:
$1)
a=-1\dfrac{2}{3}.(0,5-\dfrac{2}{3})\\
=\dfrac{-5}{3}.\left ( \dfrac{1}{2}-\dfrac{2}{3} \right )\\
=\dfrac{-5}{3}.\left ( \dfrac{3}{6}-\dfrac{4}{6} \right )\\
=\dfrac{-5}{3}.\dfrac{-1}{6}\\
=\dfrac{5}{18}\\
b=1\dfrac{13}{15}.(0,5)^2.3\\
=\dfrac{28}{15}.\left (\dfrac{1}{2} \right )^2.3\\
=\dfrac{28}{5}.\dfrac{1}{4}\\
=\dfrac{7}{5}$
Vậy 20% của a$=\dfrac{20}{100}.\dfrac{5}{18}=\dfrac{1}{5}.\dfrac{5}{18}=\dfrac{1}{18}$
$\dfrac{5}{8}$ của b $=\dfrac{5}{8}.\dfrac{7}{5}=\dfrac{7}{8}$
2)
$M=2\dfrac{2}{9}:\left ( -1\dfrac{1}{9} \right )-\dfrac{46}{5}.\dfrac{5}{23}\\
=\dfrac{20}{9}:\dfrac{-10}{9} -\dfrac{46}{23}\\
=\dfrac{20}{9}.\dfrac{-9}{10}-2\\
=-2-2\\
=-4\\
N=(-2)^3.\left ( \dfrac{3}{4}-0,25 \right ):\left ( 2\dfrac{1}{4}-1\dfrac{1}{6}\right )\\
=(-8).\left ( \dfrac{3}{4}-\dfrac{1}{4} \right ):\left ( \dfrac{9}{4}-\dfrac{7}{6} \right )\\
=(-8).\dfrac{2}{4}:\left ( \dfrac{54}{24}-\dfrac{28}{24} \right )\\
=(-4):\dfrac{26}{24}\\
=(-4):\dfrac{13}{12}\\
=(-4).\dfrac{12}{13}
=\dfrac{-48}{13}$
Vậy $\dfrac{3}{4}$ của M $=\dfrac{3}{4}.(-4)=-3$
$\dfrac{4}{3}$ của N $=\dfrac{4}{3}.\dfrac{-48}{13}=\dfrac{-64}{13}$
