Упр.105 Часть 2 ГДЗ Дорофеев Петерсон 6 класс (Математика)
1) 5/8=15/a;
2) b/7=5/3;
3) 2:c=5:7;
4) 0,3:2=d:8;
5) k/0,5=4:11;
6) 9:2=n/5;
7) 1/3 :4=x/6;
8) 0,8/y=2:3/4.
1) $$\frac{5}{8}=\frac{15}{a}$$
$$5a=8\cdot 15$$
$$a=\frac{8\cdot 15}{5}=24$$
2) $$\frac{b}{7}=\frac{5}{3}$$
$$3b=7\cdot 5$$
$$b=\frac{7\cdot 5}{3}=\frac{35}{3}=11\frac{2}{3}$$
3) $$2:c=5:7$$
$$\frac{2}{c}=\frac{5}{7}$$
$$5c=2\cdot 7$$
$$c=\frac{14}{5}=2{,}8$$
4) $$0{,}3:2=d:8$$
$$\frac{0{,}3}{2}=\frac{d}{8}$$
$$2d=0{,}3\cdot 8$$
$$d=\frac{0{,}3\cdot 8}{2}=1{,}2$$
5) $$\frac{k}{0{,}5}=4:11$$
$$\frac{k}{0{,}5}=\frac{4}{11}$$
$$11k=0{,}5\cdot 4$$
$$k=\frac{0{,}5\cdot 4}{11}=\frac{2}{11}$$
6) $$9:2=\frac{n}{5}$$
$$\frac{9}{2}=\frac{n}{5}$$
$$2n=9\cdot 5$$
$$n=\frac{45}{2}=22{,}5$$
7) $$\frac{1}{3}:4=\frac{x}{6}$$
$$\frac{1}{3}\cdot \frac{1}{4}=\frac{x}{6}$$
$$x=\frac{\frac{1}{3}\cdot 6}{4}=\frac{2}{4}=0{,}5$$
8) $$\frac{0{,}8}{y}=2:\frac{3}{4}$$
$$\frac{0{,}8}{y}=\frac{2}{\frac{3}{4}}$$
$$\frac{0{,}8}{y}=\frac{8}{3}$$
$$8y=0{,}8\cdot 3$$
$$y=\frac{0{,}8\cdot 3}{8}=0{,}3$$
Ответ
$$a=24,\quad b=11\frac{2}{3},\quad c=2{,}8,\quad d=1{,}2,\quad k=\frac{2}{11},\quad n=22{,}5,\quad x=0{,}5,\quad y=0{,}3.$$
