Решебник по математике 6 класс Мерзляк ФГОС Задание 620

 

\[\boxed{\mathbf{620\ (620)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]

Пояснение.

Решение.

\[1)\ 7\frac{1}{2}\ :4\frac{1}{2} = x\ :\frac{3}{25}\]

\[4\frac{1}{2}x = 7\frac{1}{2} \cdot \frac{3}{25}\]

\[\frac{9}{2}x = \frac{15}{2} \cdot \frac{3}{35}\]

\[\frac{9}{2}x = \frac{9}{10}\]

\[x = \frac{9}{10}\ :\frac{9}{2} = \frac{9}{10} \cdot \frac{2}{9}\]

\[x = \frac{1}{5}\]

\[Ответ:\frac{1}{5}.\]

\[2)\ \frac{24}{x + 2} = \frac{1}{5}\]

\[(x + 2) \cdot 1 = 24 \cdot 5\]

\[x + 2 = 120\]

\[x = 120 - 2\]

\[x = 118\]

\[Ответ:118.\]

\[3)\ \frac{y - 5}{6} = \frac{4}{3}\]

\[3 \cdot (y - 5) = 4 \cdot 6\]

\[3y - 15 = 24\]

\[3y = 24 + 15\]

\[3y = 39\]

\[y = 13\]

\[Ответ:13.\]

\[4)\ \frac{2}{5} = \frac{6}{x + 3}\]

\[2 \cdot (x + 3) = 6 \cdot 5\]

\[2x + 6 = 30\]

\[2x = 30 - 6\]

\[2x = 24\]

\[x = 12\]

\[Ответ:12.\]

\[5)\ \frac{5}{6} = \frac{15}{2x - 3}\]

\[5 \cdot (2x - 3) = 15 \cdot 6\]

\[10x - 15 = 90\]

\[10x = 90 + 15\]

\[10x = 105\]

\[x = \frac{105}{10}\]

\[x = 10,5\]

\[Ответ:10,5.\]

\[6)\ 12\ :\frac{4}{5}x = 20\ :\frac{1}{4}\]

\[20 \cdot \frac{4}{5}x = 12 \cdot \frac{1}{4}\]

\[16x = 3\]

\[x = 3\ :6 = \frac{3}{16}\]

\[Ответ:\ \frac{3}{16}.\]

\[\boxed{\mathbf{620.}\mathbf{\ }}\]

\[15\% = 0,15\]

\[1)\ 2400 \cdot 0,15 =\]

\[= 360\ (л) - потратил\ за\ \]

\[первую\ неделю.\]

\[2)\ 2400 - 360 =\]

\[= 2040\ (л) - осталось\]

\[\ через\ неделю.\]

\[3)\ 2040 \cdot 0,15 =\]

\[= 306\ (л) - потратил\ за\]

\[\ вторую\ неделю.\]

\[4)\ 2040 - 306 =\]

\[= 1734\ (л) - осталось\ через\ \]

\[две\ недели.\]

\[Ответ:2040\ л;\ \ 1734\ л.\]