Question

Найдите значение выражения 3/4-9/20÷3/7
9/16÷(-3/40)+4,7
(1/12-1 2/15)×6 2/3

Answer 1

Ответ:

Пошаговое объяснение:

$1) \dfrac{3}{4} -\dfrac{9}{20} :\dfrac{3}{7} =\dfrac{3}{4} -\dfrac{9}{20} \cdot \dfrac{7}{3} = \dfrac{3}{4} - \dfrac{3\cdot3\cdot7 }{20\cdot 3} =\dfrac{3}{4} -\dfrac{21}{20}=\dfrac{3}{4} -1\dfrac{1}{20} =-\left( 1\dfrac{1}{20}-\dfrac{3}{4} \right) = \\- \left( 1\dfrac{1}{20}^{\backslash1}-\dfrac{3}{4}^{\backslash5} \right) =-1\dfrac{1-15}{20} =- \dfrac{20+1-15}{20} =-\dfrac{6}{20} =-\dfrac{3}{10} =-0,3$

$2) \dfrac{9}{16} :\left(- \dfrac{3}{40} \right)+4,7=\dfrac{9}{16} \cdot\left(- \dfrac{40}{3} \right)+4,7= -\dfrac{3\cdot3\cdot 8\cdot5}{2\cdot8\cdot3} +4,7= \\\\=-\dfrac{15}{2} +4,7=-7,5+4,7=-(7,5-4,7) =- 2,8;$

$3) \left( \dfrac{1}{12} - 1\dfrac{2}{15} \right )\cdot 6\dfrac{2}{3} =- \left( 1\dfrac{2}{5}^{\backslash12}- \dfrac{1}{12}^{\backslash5} \right )\cdot 6\dfrac{2}{3}=-1\dfrac{24-5}{60} \cdot 6\dfrac{2}{3}=- 1\dfrac{19}{60} \cdot 6\dfrac{2}{3}=\\\\=-\dfrac{79}{60} \cdot \dfrac{20}{3}=- \dfrac{79\cdot20}{20\cdot3\cdot 3} =-\dfrac{79}{9} =-8\dfrac{7}{9} .$