Question

tính thuận tiện

a) 2/5+3/7+3/5+4/7

b) 2/3 nhân 4/9+2/3 nhân5/9

Answer 1

a: =(2/5+3/5)+(3/7+4/7)=1+1=2

b: =2/3(4/9+5/9)=2/3

Answer 2

a)(2/5+3/5)+(3/7+4/7)=1+1=2

b)2/3x4/9+2/3x5/9=2/3x(4/9+5/9)=2/3x1=2/3

Answer 3

a \(\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{4}{7}=1+1=2\)

b \(\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{2}{3}\times1=\dfrac{2}{3}\)

Answer 4

\(a,=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\\ =1+1=2\\ b,=\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{2}{3}\times1=\dfrac{2}{3}\)

Answer 5

a, 2/5+3/7+3/5+4/7

=(2/5+3/5)+(3/7+4/7)

=        1    +      1

             =2

b) 2/3 x 4/9+2/3 x 5/9

= 2/3   x (4/9+5/9)

  =     2/3

Answer 6

a) 2/5 + 3/7 + 3/5 + 4/7

= (2/5 + 3/5) + (3/7 + 4/7)

= 1 + 1

= 2

b) 2/3 x 4/9 + 2/3 x 5/9

= ( 2/3 x 2/3) + ( 4/9 x 5/9)

= 4/9 + 20/81

Answer 7

a) \(\dfrac{2}{5}+\dfrac{3}{7}+\dfrac{3}{5}+\dfrac{4}{7}\)

\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)

\(=1+1=2\)

b) \(\dfrac{2}{3}\times\dfrac{4}{9}+\dfrac{2}{3}\times\dfrac{5}{9}\)

\(=\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=\dfrac{2}{3}\times1\)

\(=\dfrac{2}{3}\)

Answer 8

a = 2

b =2/3