Question

Tính bằng 2 cách :

                                 ( 2/5 + 1/2 ) x 1/4 

Answer 1

\(\left\{{}\begin{matrix}C_1:=\left(\dfrac{4}{10}+\dfrac{5}{10}\right)\times\dfrac{1}{4}=\dfrac{9}{10}\times\dfrac{1}{4}=\dfrac{9}{40}\\C_2=\dfrac{2}{5}\times\dfrac{1}{4}+\dfrac{1}{2}\times\dfrac{1}{4}=\dfrac{1}{10}+\dfrac{3}{4}=\dfrac{9}{10}\end{matrix}\right.\)

Answer 2

Cách 1)

Cách 2)

\(\dfrac{2}{5}+\dfrac{1}{2}x\dfrac{1}{4}=\)\(\dfrac{2}{5}x\dfrac{1}{4}+\dfrac{1}{2}x\dfrac{1}{4}=\dfrac{1}{10}+\dfrac{1}{8}=\dfrac{9}{40}\)

 

Answer 3

C1 =9/10x1/4=9/40

C2 =2/5x1/4+1/2x1/4=1/10+1/8=9/40