Упражнение 765

Решение:

• $${\largeа)}\ \frac{ (2{,}3+5{,}8)\cdot3\frac{5}{7}}{ (4{,}9-2{,}3):\frac{7}{9}}=\frac{8{,}1\cdot\frac{26}{7}}{2{,}6\cdot\frac{9}{7}}=\frac{8{,}1\cdot\frac{26\phantom{^{\backslash1}}}{\cancel7^{\backslash1}}\cdot\cancel7^{\backslash1}}{2{,}6\cdot\frac{9\phantom{^{\backslash1}}}{\cancel7^{\backslash1}}\cdot\cancel7^{\backslash1}}=\frac{\cancel{8{,}1}^{\backslash0{,}9}\cdot\cancel{26}^{\backslash10}}{\cancel{2{,}6}^{\backslash1}\cdot\cancel9^{\backslash1}}=0{,}9\cdot10=9$$

• $${\largeб)}\ \frac{\frac{1}{8}:\frac{5}{16}+2{,}25\cdot0{,}8}{\left(2\frac{1^{\backslash3}}{48\phantom{^{\backslash3}}}-1\frac{55^{\backslash2}}{72\phantom{^{\backslash2}}}\right):3\frac{1}{12}}+3\frac{3}{5}=\frac{\frac{1\phantom{^{\backslash1}}}{\cancel8^{\backslash1}}\cdot\frac{\cancel{16}^{\backslash2}}{5\phantom{^{\backslash2}}}+1{,}8}{\left(2\frac{3}{144}-1\frac{110}{144}\right):\frac{37}{12}}+3\frac{3}{5}=\frac{\frac{2}{5}+1{,}8}{\left(1\frac{147}{144}-1\frac{110}{144}\right)\cdot\frac{12}{37}}+3\frac{3}{5}=\frac{0{,}4+1{,}8}{\frac{\cancel{37}^{\backslash1}}{\cancel{144}^{\backslash12}}\cdot\frac{\cancel{12}^{\backslash1}}{\cancel{37}^{\backslash1}}}+3{,}6=\frac{2{,}2}{\frac{1}{12}}+3{,}6=\frac{2{,}2\cdot12}{\frac{1\phantom{^{\backslash1}}}{\cancel{12}^{\backslash1}}\cdot\cancel{12}^{\backslash1}}+3{,}6=26{,}4+3{,}6=30$$

• $${\largeв)}\ \frac{0{,}21\cdot1{,}25}{13{,}6-11{,}1}=\frac{0{,}21\cdot1{,}25}{2{,}5}=\frac{0{,}21\cdot1{,}25\cdot10}{2{,}5\cdot10}=\frac{0{,}21\cdot\cancel{12{,}5}^{\backslash0{,}5}}{\cancel{25}^{\backslash1}}=0{,}21\cdot0{,}5=0{,}105$$

• $${\largeг)}\ \frac{2{,}781}{2{,}06}+\frac{7{,}825}{3{,}13}=1{,}35+2{,}5=3{,}85$$