Bài tập 4 trang 66 vbt Toán 4 tập 2 Cánh diều
a) Tính rồi so sánh:
$(\frac{1}{4}\times \frac{2}{3})\times \frac{3}{5}$ …… $\frac{1}{4}\times (\frac{2}{3}\times \frac{3}{5})$
$(\frac{1}{2}\times \frac{1}{6})\times \frac{1}{5}$ …… $\frac{1}{2}\times (\frac{1}{5}\times \frac{1}{6})$
b) Viết ví dụ trương tự câu a rồi đố bạn thực hiện.
Bài Làm:
a)
$(\frac{1}{4}\times \frac{2}{3})\times \frac{3}{5}=\frac{2}{12}\times \frac{3}{5}=\frac{1}{6}\times \frac{3}{5}=\frac{3}{30}=\frac{1}{10}$
$\frac{1}{4}\times (\frac{2}{3}\times \frac{3}{5})=\frac{1}{4}\times \frac{2}{5}=\frac{2}{20}=\frac{1}{10}$
Vậy $(\frac{1}{4}\times \frac{2}{3})\times \frac{3}{5}$ = $\frac{1}{4}\times (\frac{2}{3}\times \frac{3}{5})$.
$(\frac{1}{2}\times \frac{1}{6})\times \frac{1}{5}=\frac{1}{12}\times \frac{1}{5}=\frac{1}{60}$
$\frac{1}{2}\times (\frac{1}{5}\times \frac{1}{6})=\frac{1}{2}\times \frac{1}{30}=\frac{1}{60}$
Vậy $(\frac{1}{2}\times \frac{1}{6})\times \frac{1}{5}$ = $\frac{1}{2}\times (\frac{1}{5}\times \frac{1}{6})$.
b) Ví dụ:
$(\frac{1}{3}\times \frac{2}{3})\times \frac{4}{5}=\frac{2}{9}\times \frac{4}{5}=\frac{8}{45}$
$\frac{1}{3}\times (\frac{2}{3}\times \frac{4}{5})=\frac{1}{3}\times \frac{8}{15}=\frac{8}{45}$
Vậy $(\frac{1}{3}\times \frac{2}{3})\times \frac{4}{5}$ = $\frac{1}{3}\times (\frac{2}{3}\times \frac{4}{5})$.
