Question

tính 2 cách 

(2/5+1/2)x1/4 

Answer 1

\(C1:\left(\dfrac{2}{5}+\dfrac{1}{2}\right)\times\dfrac{1}{4}=\dfrac{9}{10}\times\dfrac{1}{4}=\dfrac{9}{40}\\ C2:\left(\dfrac{2}{5}+\dfrac{1}{2}\right)\times\dfrac{1}{4}=\dfrac{2}{5}\times\dfrac{1}{4}+\dfrac{1}{2}\times\dfrac{1}{4}\\ =\dfrac{1}{10}+\dfrac{1}{8}\\ =\dfrac{9}{40}\)

Answer 2

c1 : = 9/10 x 1/4 

= 9/40

c2 : = 2/5 x 1/4 + 1/2 x 1/4

= 1/10 + 1/8 

= 9/40

Answer 3

=(4/10+5/10)x1/4

=9/10x1/4=9/40