Question

Tinh 

2/5 + 4/5 ÷ 4

3/8 × 7/4 - 3/8

6/5 - 3 ÷ 15/4

 

Answer 1

\(\dfrac{2}{5}+\dfrac{4}{5}:4=\dfrac{2}{5}+\dfrac{1}{5}=\dfrac{3}{5}\)

\(\dfrac{3}{8}\times\dfrac{7}{4}-\dfrac{3}{8}=\dfrac{3}{8}\left(\dfrac{7}{4}-1\right)=\dfrac{3}{8}\times\dfrac{3}{4}=\dfrac{9}{32}\)

\(\dfrac{6}{5}-3:\dfrac{15}{4}=\dfrac{6}{5}-\dfrac{4}{5}=\dfrac{2}{5}\)

Answer 2

\(=\dfrac{2}{5}+\dfrac{4}{5}\times\dfrac{1}{4}\\ =\dfrac{2}{5}+\dfrac{1}{5}\\ =\dfrac{3}{5}\\ \\ =\dfrac{3}{8}\times\dfrac{7}{4}-\dfrac{3}{8}\times1\\ =\dfrac{3}{8}\times\left(\dfrac{7}{4}-1\right)\\ =\dfrac{3}{8}\times\dfrac{3}{4}\\ =\dfrac{9}{32}\\\\ =\dfrac{6}{5}-3\times\dfrac{4}{15}\\ =\dfrac{6}{5}-\dfrac{4}{5}\\ =\dfrac{2}{5}\)

Answer 3

\(\dfrac{2}{5}+\dfrac{4}{5}:4=\dfrac{2}{5}+\dfrac{1}{5}=\dfrac{3}{5}\\ \dfrac{3}{8}\times\dfrac{7}{4}-\dfrac{3}{8}=\dfrac{3}{8}\times\dfrac{7}{4}-\dfrac{3}{8}\times1=\dfrac{3}{8}\times\left(\dfrac{7}{4}-1\right)=\dfrac{3}{8}\times\dfrac{3}{4}=\dfrac{9}{32}\\ \dfrac{6}{5}-3:\dfrac{15}{4}=\dfrac{6}{5}-\dfrac{4}{5}=\dfrac{2}{5}\)