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= 51/20
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= 3/14
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= 4/7 - 2/7
= 2/7
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= 17/45
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= 2/3
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= 2 x 1/4
= 1/2
` 1/2 + 3/4 - 5/6 = 6/12 + 9/12 - 10/12 = 5/12`
` ( 5/6 + 3/8) xx 2/7 = ( 15/24 + 9/24) xx 2/7 = 29/24 xx 2/7 = 29/84`
` ( 7/6 - 3/4) : 3/5 = ( 14/12 - 9/12) : 3/5 = 5/12 : 3/5 = 5/12 xx 5/3 = 25/36`
` 6/7 xx 2/3 : 5/7 = 6/7 xx 2/3 xx 7/5 = 4/5`
`1/7+5/6+4/7+3/6+2/7+4/6`
`=(1/7 + 4/7 + 2/7 )+(5/6 + 3/6 +4/6)`
`= 7/7 + 12/6`
`=1+2`
`=3`
`1/7+5/6+4/7+3/6+2/7+4/6`
`=(1/7+4/7+2/7)+(5/6+3/6+4/6)`
`=7/7+12/6`
`=1+2`
`=3`
Bài 5:
a: =1/3+2/5
=5/15+6/15
=11/15
b: =6/21+12/21=18/21=6/7
c: =16/24+10/24
=26/24
=13/12
d: =4/12+3/12+10/12
=17/12
e: =19/24-9/24
=10/24
=5/12
f: =8/9-3/9=5/9
g: =9/3+1/3=10/3
k: =15/24+42/24+14/24
=71/24
3/7 + 4 = 3/7 + 4/1 = 31/7
5/9 x 3 =5/9 x 3/1 = 15/9 = 5/3
7/8 - 2/9 =7/8 - 2/9 =47/72
5 - 3/4 =5/1 - 3/4 = 20/4 - 3/4 = 17/4
5/7 : 6 = 5/7 : 6/1 = 5/7 x 1/6 = 5/42
5/6 x 2/7 =10/42= 5/21
3 + 3/4 = 3/1 + 3/4 = 12/4+ 3/4 =15/4
3/5 x 4/8 =12/40 = 3/10.
5 : 3/8 = 5/1 : 3/8 = 5/1 x 8/5 = 8/1= 8
3 x 5/9 =3/1 x 5/9 = 15/9=5/3
\(\dfrac{3}{4}\times\dfrac{4}{5}\times\dfrac{5}{6}\times\dfrac{6}{7}\div\dfrac{1}{7}\)
\(=\dfrac{3}{4}\times\dfrac{4}{5}\times\dfrac{5}{6}\times\dfrac{6}{7}\times\dfrac{7}{1}\)
\(=\dfrac{3\times4\times5\times6\times7}{4\times5\times6\times7\times1}\)
\(=\dfrac{3}{1}=3\)
a,Cách 1: (6/11 + 5/11 ) x 3/7 Cách 2 :(6/11 + 5/11) x 3/7
= 1 x 3/7 =6/11 x 3/7 + 5/11 x 3/7
= 3/7 = 18/77 + 15/77
= 3/7
b, Cách 1:3/5 x 7/9 - 3/5 x 2/9 Cách 2 :3/5 x 7/9 - 3/5 x 2/9
= 7/15 - 2/15 = 3/5 x (7/9 - 2/9 )
= 1/3 = 3/5 x 5/9
= 1/3
c, Cách 1:(6/7 - 4/7) : 2/5 Cách 2: ( 6/7- 4/7 ) : 2/5
= 2/7 : 2/5 = 6/7 : 2/5 - 4/7 : 2/5
= 5/7 = 15/7 - 10/7
= 5/7
d,Cách 1:8/15 : 2/11 + 7/15 : 2/11 Cách 2:8/15 : 2/11 +7/15 : 2/11
= 88/30 + 77/30 =(8/15+7/15) :2/11
= 11/2 = 1 : 2/11
= 11/2
Bài 2 cậu tự làm nhé !
Hướng dẫn giải: