Упр.360 ГДЗ Мерзляк Полонский 6 класс (Математика)

1) 3/8x+ 4/9x? 5/12x, если x = 3 3/29 ;
2) 9/10с ? 2/15с? 3/5с, если с = 2,4;
3) 3*3/5y?2*1/3y? 1/15y, если y = 10.

1) При $$x=3\frac{3}{29}=\frac{90}{29}$$:

$$ \frac{3}{8}x+\frac{4}{9}x-\frac{5}{12}x = \frac{27}{72}x+\frac{32}{72}x-\frac{30}{72}x = \frac{29}{72}x $$
$$ \frac{29}{72}\cdot \frac{90}{29} = \frac{90}{72} = \frac{5}{4} = 1\frac{1}{4} $$

2) При $$c=2{,}4=\frac{24}{10}=\frac{12}{5}$$:

$$ \frac{9}{10}c-\frac{2}{15}c-\frac{3}{5}c = \frac{27}{30}c-\frac{4}{30}c-\frac{18}{30}c = \frac{5}{30}c = \frac{1}{6}c $$
$$ \frac{1}{6}\cdot \frac{12}{5} = \frac{2}{5} $$

3) При $$y=10$$:

$$ 3\frac{3}{5}y-2\frac{1}{3}y-\frac{1}{15}y = \frac{18}{5}y-\frac{7}{3}y-\frac{1}{15}y = \frac{54}{15}y-\frac{35}{15}y-\frac{1}{15}y = \frac{18}{15}y = \frac{6}{5}y $$
$$ \frac{6}{5}\cdot 10=12 $$

Ответ

1) $$1\frac{1}{4}$$; 2) $$\frac{2}{5}$$; 3) $$12$$.