Tính bằng hai cách: (2/5 + 1/2) x 1/4

$Wally$

Đáp án + Giải thích các bước giải:

$C1$: $(\dfrac{2}{5}$ $+$ $\dfrac{1}{2})$ $\times$ $\dfrac{1}{4}$

= $(\dfrac{4}{10}$ $+$ $\dfrac{5}{10})$ $\times$ $\dfrac{1}{4}$

= $\dfrac{9}{10}$ $\times$ $\dfrac{1}{4}$

= $\dfrac{9}{40}$ 

$C2$: $(\dfrac{2}{5}$ $+$ $\dfrac{1}{2})$ $\times$ $\dfrac{1}{4}$

= $\dfrac{2}{5}$ $\times$ $\dfrac{1}{4}$ $+$ $\dfrac{1}{2}$ $\times$ $\dfrac{1}{4}$

= $\dfrac{1}{10}$ $+$ $\dfrac{1}{8}$

= $\dfrac{8}{80}$ $+$ $\dfrac{10}{80}$

= $\dfrac{18}{80}$

= $\dfrac{9}{40}$