a) \(1\dfrac{7}{20}:2,7+2,7:1,35\)

\(=1,35:2,7+2,7:1,35\)

\(=0,5+2\)

\(=2,5\)

b) \(3\dfrac{1}{2}-\left(0,4:2\dfrac{1}{2}\right).\left(4,2-1\dfrac{3}{4}\right)\)

\(=\dfrac{7}{2}-\left(0,4:\dfrac{5}{2}\right).\left(4,2-\dfrac{7}{4}\right)\)

\(=\dfrac{7}{2}-\dfrac{4}{25}.\dfrac{49}{20}\)

\(=\dfrac{7}{2}-\dfrac{49}{125}\)

\(=\dfrac{777}{250}\)

a) \(1\dfrac{7}{20}:2,7+2,7:1,35+\left(0,4:2\dfrac{1}{2}\right).\left(4,2-1\dfrac{3}{40}\right)\)

\(=\dfrac{27}{20}:\dfrac{27}{10}+\dfrac{27}{10}:\dfrac{27}{10}+\left(\dfrac{2}{5}:\dfrac{5}{2}\right).\left(\dfrac{21}{5}-\dfrac{43}{40}\right)\)

\(=1+1+\dfrac{4}{25}.\dfrac{25}{8}\)

\(=2+\dfrac{1}{2}\)

\(=2\dfrac{1}{2}\)

b) \(\left(6\dfrac{3}{5}-3\dfrac{3}{14}\right).5\dfrac{5}{6}:\left(21-1.25\right):2,5\)

\(=\left(\dfrac{33}{5}-\dfrac{45}{14}\right).\dfrac{35}{6}:\left(-4\right):2,5\)

\(=\left(\dfrac{462}{60}-\dfrac{225}{60}\right).\dfrac{35}{6}.\dfrac{1}{-4}:\dfrac{5}{2}\)

\(=\dfrac{237}{60}.\dfrac{35}{6}.\dfrac{1}{-4}.\dfrac{2}{5}\)

\(=\dfrac{3.79.7.5.2}{5.14.3.2.\left(-4\right).5}\)

\(=\dfrac{79.7}{14.\left(-4\right).5}=\dfrac{553}{-280}\) (số xấu :v)

c) \(\dfrac{0,125-\dfrac{1}{5}+\dfrac{1}{7}}{0,375-\dfrac{3}{5}+\dfrac{3}{7}}+\dfrac{\dfrac{1}{2}+\dfrac{1}{3}-0,2}{\dfrac{3}{4}+0,5-\dfrac{3}{10}}\)

\(=\dfrac{0,125-\dfrac{1}{5}+\dfrac{1}{7}}{3\left(0,125-\dfrac{1}{5}+\dfrac{1}{7}\right)}+\dfrac{\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{5}}{\dfrac{3}{4}+\dfrac{1}{2}-\dfrac{3}{10}}\)

\(=\dfrac{1}{3}+\dfrac{\dfrac{30}{60}+\dfrac{20}{60}-\dfrac{12}{60}}{\dfrac{45}{60}+\dfrac{30}{60}-\dfrac{9}{60}}\)

\(=\dfrac{1}{3}+\dfrac{\dfrac{19}{30}}{\dfrac{11}{10}}\)

\(=\dfrac{1}{3}+\dfrac{19}{33}\)

\(=\dfrac{11}{33}+\dfrac{19}{33}=\dfrac{30}{33}=\dfrac{10}{11}\)

a: \(=-15,5\left(20,8+9,2\right)+3,5\left(9,2+20,8\right)\)

\(=30\cdot\left(-12\right)=-360\)

b: \(=\dfrac{21}{20}:\dfrac{27}{10}+2+\left(\dfrac{2}{5}:\dfrac{5}{2}\right)\cdot\left(\dfrac{21}{5}-\dfrac{13}{10}\right)\)

\(=\dfrac{21}{10}\cdot\dfrac{10}{27}+2+\dfrac{4}{25}\cdot\dfrac{29}{10}\)

\(=\dfrac{7}{9}+2+\dfrac{58}{125}=\dfrac{3647}{1125}\)

\(B=1x\frac{7}{20}:2,7+2,7:1,35+\left(0,4+2\frac{1}{2}\right)x\left(4,2-1\frac{3}{10}\right)\)

\(B=\frac{7}{20}:2,7+2+2,9x2,9\)

\(B=\frac{7}{54}+2+8,41\)

\(B=10,53962963\)

Câu 1: A

Câu 2: C

Câu 3: 1/4 quả dưa nặng 0,5kg

Câu 4: =-3-1,3+5,6=4,3-3=1,3

\(\dfrac{5}{12}+\dfrac{-7}{12}=\dfrac{-2}{12}=\dfrac{-1}{6}\)

\(\dfrac{1}{2}+\dfrac{-2}{3}=\dfrac{3}{6}+\dfrac{-4}{6}=\dfrac{-1}{6}\)

\(\dfrac{3}{5}-\dfrac{4}{3}=\dfrac{9}{15}-\dfrac{20}{15}=\dfrac{-11}{15}\)

\(\dfrac{-15}{14}.\dfrac{21}{20}=\dfrac{-315}{280}=\dfrac{-9}{8}\)

\(\dfrac{-1}{6}\)

\(\dfrac{-1}{6}\)

\(\dfrac{-11}{15}\)

\(\dfrac{-9}{8}\)

a: =11+3/4-6-5/6+4+1/2+1+2/3

=10+9/12-10/12+6/12+8/12

=10+13/12=133/12

b: \(=2+\dfrac{17}{20}-1-\dfrac{11}{15}+2+\dfrac{3}{20}\)

=3-11/15

=34/15

c: \(=\dfrac{31}{7}:\left(\dfrac{7}{5}\cdot\dfrac{31}{7}\right)\)

\(=\dfrac{31}{7}:\dfrac{31}{5}=\dfrac{5}{7}\)

d: \(=\dfrac{29}{8}\cdot\dfrac{36}{29}\cdot\dfrac{15}{23}\cdot\dfrac{23}{5}=\dfrac{9}{2}\cdot3=\dfrac{27}{2}\)