Question

tính bằng hai cách :

a( 1/2+1/3) x 2/5

3/5 x 17/21+17/21x2/5

           ai nhanh thì tặng 1 tick

Answer 1

a c1 (1/2+1/3)x2/5

=5/6x2/5

=1/3

c2 1/2 x2/5+1/3x2/5

=1/5+2/15

=1/3

Answer 2

a) Cách 1 :

 \(\left(\frac{1}{2}+\frac{1}{3}\right)\times\frac{2}{5}\)

= \(\left(\frac{3}{6}+\frac{2}{6}\right)\times\frac{2}{5}\)

= \(\frac{5}{6}\times\frac{2}{5}\)

= \(\frac{10}{30}=\frac{1}{3}\)

Cách 2 :

 \(\left(\frac{1}{2}+\frac{1}{3}\right)\times\frac{2}{5}\)

= \(\frac{1}{2}\times\frac{2}{5}+\frac{1}{3}\times\frac{2}{5}\)

= \(\frac{2}{10}+\frac{2}{15}\)

= \(\frac{10}{30}=\frac{1}{3}\)

b) Cách 1 :

\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)

= \(\frac{51}{105}+\frac{34}{105}\)

= \(\frac{85}{105}=\frac{17}{21}\)

Cách 2 : 

\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)

= \(\left(\frac{3}{5}+\frac{2}{5}\right)\times\frac{17}{21}\)

= \(1\times\frac{17}{21}\)

= \(\frac{17}{21}\)

Nếu đúng thì mọi người t i c k em nhé:3