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a)\(\frac{2}{3}\times\frac{4}{5}-\frac{3}{5}\times\frac{1}{2}=\frac{8}{15}-\frac{3}{10}\)
\(=\frac{7}{30}\)
b) \(\frac{12}{5}-\frac{4}{7}-\frac{3}{7}=\frac{64}{35}-\frac{3}{7}\)
\(=\frac{7}{5}\)
cho chj nhé em THKS em nhìu!
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a)
Cách 1
3/4*1/2*2
=3/8*2
=3/4
Cách 2
3/4*1/2*2
=3/4*(1/2*2)
=3/4*1
=3/4
b)
Cách 1
(3/4+1/2)*5/7
=5/4*5/7
=25/28
Cách 2
(3/4+1/2)*5/7
=3/4*5/7+5/7*1/2
=15/28+5/14
=25/28
c)
Cách 1
5/7*13/21+2/7*13/21
=65/147+26/147
=13/21
cách 2
5/7*13/21+2/7*13/21
=13/21*(2/7+5/7)
=13/21*1
=13/21
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1: Tính
a, 1/2 x 2/3 x 3/4 = 1/4
b, 7/8 x 8/9 x 9/10 = 7/10
c, 5/14 x 7/15 x 28/7 = 2/3
d, 2 x 1/2 x 3 x 1/3 x 4 x 1/4 x 5 x 1/5 = 1
Bài 2: Tính
a, 7/20 - ( 5/8 - 3/5 ) = 7/20 - 1/40 = 14/40 - 1/40 = 13/40
b, 5/6 + ( 5/9 - 1/4 ) = 5/6 + 11/36 = 30/36 + 11/36 = 41/36
c, 9/10 - ( 2/5 + 3/10 ) + 7/20 = 9/10 - 7/10 + 7/20 = 2/10 + 7/20 = 4/20 + 7/20 = 11/20.
Bài 3: Tìm x:
a, 1/2 + x = 5/6
x = 5/6 - 1/2
x = 1/3
b, 5/6 - x = 1/3
x = 5/6 - 1/3
x = 1/2
c, x - 1/mấy vậy bạn
d, 1/3 x x = 1/6
x = 1/6 : 1/3
x = 1/2
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
a.3+2/5
=15/5+2/5
=17/5
b.4-5/7
=28/7-5/7
=23/7
c.1-(2/5+1/3)
=1-11/15
=4/15
a)3+2/5=17/5
b) a-5/7=17/5-5/7=94/35
c)1-(2/5+1/3)=4/15