Question

Tính nhanh: 2/5x1/2+2/5x4/3+2/5x1/6+2/5

Answer 1

\(=\dfrac{2}{5}\left(\dfrac{1}{2}+\dfrac{4}{3}+\dfrac{1}{6}+1\right)\\ =\dfrac{2}{5}.\left(\dfrac{3+4.2+1+6}{6}\right)\\ =\dfrac{2}{5}.3\\ =\dfrac{6}{5}\)

Answer 2

`(2)/(5)xx(1)/(2)+(2)/(5)xx(4)/(3)+(2)/(5)xx(1)/(6)+(2)/(5)`

`=(2)/(5)xx((1)/(2)+(4)/(3)+(1)/(6)+1)`

`=(2)/(5)xx(1xx3+4xx2+1+1xx6)/(6)`

`=(2)/(5)xx(3+8+1+6)/(2xx3)`

`=(2)/(5)xx(18)/(2xx3)`

`=(18)/(5xx3)=(18)/(15)`

Answer 3

2/5x1/2+2/5x4/3+2/5x1/6+2/5

=\(\dfrac{2}{5}x\left(\dfrac{1}{2}+\dfrac{4}{3}+\dfrac{1}{6}+1\right)\)=\(\dfrac{2}{5}x3\)=\(\dfrac{6}{5}\)