Tính. a) 1/6 : 3/7 b) 5/12 : 1/4 c) 4/15 : 8/3 d) 18/5 : 9/10

Giải Toán lớp 4 Bài 75: Phép chia phân số

Toán lớp 4 Tập 2 trang 67 Bài 2: Tính.

Lời giải:

a) $\frac{1}{6}:\frac{3}{7}\text{=}\frac{1}{6}\times \frac{7}{3}\text{=}\frac{1\times 7}{6\times 3}\text{=}\frac{7}{18}$

b) $\frac{5}{12}:\frac{1}{4}\text{=}\frac{5}{12}\times \frac{4}{1}\text{=}\frac{5\times 4}{12\times 1}\text{=}\frac{20}{12}\text{=}\frac{5}{3}$

c) $\frac{4}{15}:\frac{8}{3}\text{=}\frac{4}{15}\times \frac{3}{8}\text{=}\frac{4\times 3}{15\times 8}\text{=}\frac{12}{120}\text{=}\frac{1}{10}$

d) $\frac{18}{5}:\frac{9}{10}\text{=}\frac{18}{5}\times \frac{10}{9}\text{=}\frac{18\times 10}{5\times 9}\text{=}\frac{180}{45}\text{=}4$