# Giải bài 60 trang 31 - Sách giáo khoa Toán 7 tập 1

##### Hướng dẫn giải

a) $$\dfrac{1}{3}x : \dfrac{2}{3}= 1\dfrac{3}{4} :\dfrac{2}{5} \Rightarrow \dfrac{x}{3}:\dfrac{2}{3} = \dfrac{7}{4}:\dfrac{2}{5} \Rightarrow \dfrac{x}{3} = \dfrac{\dfrac{7}{4}.\dfrac{2}{3}}{\dfrac{2}{5}} \Rightarrow \dfrac{x}{3} = \dfrac{7}{6}.\dfrac{5}{2}$$

$$\Rightarrow \dfrac{x}{3} = \dfrac{35}{12} \Rightarrow x = \dfrac{35.3}{12} \Rightarrow x = \dfrac{35}{4} = 8\dfrac{3}{4}$$

b) 4,5 : 0,3 = 2,25 : (0,1.x) $$\Rightarrow$$ 0,1.x = $$\dfrac{2,25.0,3}{4,5}$$

$$\Rightarrow$$ 0,1.x = 0,15 $$\Rightarrow$$ x = 1,5

c) 8 : $$(\dfrac{1}{4}.x)$$ = 2 : 0,02 $$\Rightarrow$$ $$\dfrac{x}{4} = \dfrac{8.0,02}{2} \Rightarrow \dfrac{x}{4} = 0,08$$

$$\Rightarrow$$ x = 0,08.4 $$\Rightarrow$$ x = 0,32

d) 3 : 2 $$\dfrac{1}{4}$$ = $$\dfrac{3}{4}$$ : (6.x) $$\Rightarrow$$ 3 : $$\dfrac{9}{4} = \dfrac{3}{4}$$ : (6.x) $$\Rightarrow$$ 6.x = $$\dfrac{ \dfrac{3}{4}.\dfrac{9}{4}}{3}$$

$$\Rightarrow$$ 6.x = $$\dfrac{27}{16}.\dfrac{1}{3}$$ $$\Rightarrow$$ 6.x = $$\dfrac{9}{16}$$ $$\Rightarrow$$ x = $$\dfrac{9}{16}$$ : 6 $$\Rightarrow$$ x = $$\dfrac{3}{32}$$