4. Найди неизвестный член пропорции: a) y: 2,4 = 7,5: 4,5; 160 x b)= 255 7 7 c) y: 5 = 1 : 1 . 9 3 27

a) y : 2,4 = 7,5 : 4,5

$$y = \frac{2,4 \times 7,5}{4,5} = \frac{18}{4,5} = 4$$

b) $$\frac{160}{25} = \frac{x}{5}$$

$$x = \frac{160 \times 5}{25} = \frac{800}{25} = 32$$

c) $$y : 5 \frac{3}{7} = 1 \frac{7}{9} : 1 \frac{7}{27}$$

$$y : \frac{38}{7} = \frac{16}{9} : \frac{34}{27}$$

$$y = \frac{\frac{16}{9} \times \frac{38}{7}}{\frac{34}{27}} = \frac{\frac{608}{63}}{\frac{34}{27}} = \frac{608}{63} \times \frac{27}{34} = \frac{8}{7} \times \frac{3}{1} = \frac{24}{7} = 3 \frac{3}{7}$$

Ответ: а) 4; b) 32; c) $$3 \frac{3}{7}$$