Question

Answer 1

3/8 + 7/12 +10/16 +10/24

= (3/8+10/16)+(7/12+10/24)

= 1                  +       1

= 2

4/6+7/13+17/9+19/13+1/9+14/6

= (4/6+14/6)+(7/13+19/13)+(17/9+1/9)

=       3         +     2             +      2

=                         7

Answer 2

bài 6 :

a) \(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)

\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)

\(=1+1=2\)

b) \(=\left(\dfrac{4}{6}+\dfrac{14}{6}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)

\(=3+2+2=7\)

 

 

Answer 3

Bài `6:`

`a)3/8+7/12+10/16+10/24=3/8+7/12+5/8+5/12=(3/8+5/8)+(7/12+5/12)=8/8+12/12=1+1=2`

`b)4/6+7/13+17/9+19/13+1/9+14/6`

`=(4/6+14/6)+(7/13+19/13)+(17/9+1/9)`

`=18/6+26/13+18/9=3+2+2=7`

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Bài `7:`

`1/2+1/6+1/12+1/20+1/30+1/42+1/56`

`=1/[1xx2]+1/[2xx3]+1/[3xx4]+1/[4xx5]+1/[5xx6]+1/[6xx7]+1/[7xx8]`

`=1-1/2+1/2-1/3+...+1/7-1/8`

`=1-1/8=8/8-1/8=7/8`

Answer 4

bafi 6

\(a=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\\ =\dfrac{8}{8}+\dfrac{12}{12}=1+1=2\)

\(b=\left(\dfrac{4}{6}+\dfrac{14}{6}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)=\dfrac{18}{6}+\dfrac{26}{13}+\dfrac{18}{9}\\ =3+2+2=7\)

bai 7

\(=\left(\dfrac{1}{20}+\dfrac{1}{30}\right)+\left(\dfrac{1}{42}+\dfrac{1}{56}\right)+\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}\\ =\dfrac{1}{12}+\dfrac{1}{24}+\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}\\ =\left(\dfrac{1}{12}+\dfrac{1}{12}+\dfrac{1}{6}+\dfrac{1}{2}\right)+\dfrac{1}{24}\\ =\left(\dfrac{1}{6}+\dfrac{1}{6}+\dfrac{1}{2}\right)+\dfrac{1}{24}=\left(\dfrac{1}{3}+\dfrac{1}{2}\right)+\dfrac{1}{24}\\ =\dfrac{5}{6}+\dfrac{1}{24}=\dfrac{20}{24}+\dfrac{1}{24}=\dfrac{21}{24}=\dfrac{7}{8}\)