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- Tính giá trị biểu thức:
a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145
b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7
c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11
- Tính giá trị biểu thức:
a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21
b) (5/17 x 21/32 x 47/24 x 0)
= 0
c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7
- Tìm x:
a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x
b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15
c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2
- Tìm x:
a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36
câu,b,không,đủ,thông,tin,nhan,bạn.
![](https://rs.olm.vn/images/avt/0.png?1311)
`(6/11 +5/11) xx 3/7`
`= 11/11xx 3/7`
`=1xx3/7`
`=3/7`
__
`3/5 xx 7/9 - 3/5 xx 2/9`
`= 3/5 xx (7/9-2/9)`
`= 3/5 xx 5/9`
`= 15/45`
`= 1/3`
__
`(6/7 -4/7):2/5`
`= 2/7 : 2/5`
`= 2/7 xx 5/2`
`= 10/14`
`= 5/7`
\(\left(\dfrac{6}{11}+\dfrac{5}{11}\right)\times\dfrac{3}{7}\)
\(=\dfrac{11}{11}\times\dfrac{3}{7}\\ =1\times\dfrac{3}{7}=\dfrac{3}{7}\)
_____
\(\dfrac{3}{5}\times\dfrac{7}{9}-\dfrac{3}{5}\times\dfrac{2}{9}\\ =\dfrac{3}{5}\times\left(\dfrac{7}{9}-\dfrac{2}{9}\right)\\ =\dfrac{3}{5}\times\dfrac{5}{9}\\ =\dfrac{3}{9}\\ =\dfrac{1}{3}\)
_________
\(\left(\dfrac{6}{7}-\dfrac{4}{7}\right):\dfrac{2}{5}\\ =\dfrac{2}{7}\times\dfrac{5}{2}\\ =\dfrac{10}{14}\\ =\dfrac{5}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
10.213
11. 2 giờ 55 phút
12. 4 ngày 21 giờ
13.
a: 6,008
b: 4500
c: 5,628
d: 4,009
14.
a,8579 cm2
b,32,04 m2
c,187200m2
d,5,017 tấn
![](https://rs.olm.vn/images/avt/0.png?1311)
14:
a: \(85.79km^2=857900000000cm^2\)
b: \(32m^24dm^2=32.04m^2\)
c: \(1872dm^2=18.72m^2\)
d: 5 tấn 17kg=5,017 tấn
13:
a: \(6dm^38cm^3=6.008dm^3\)
b: \(4.5m^3=4500dm^3\)
c: \(5628dm^3=5.628m^3\)
d: \(4m^39dm^3=4.009m^3\)
12: =108h:3+80h
=36h+80h=116h
10:
3h18p+7h21p:3
=198p:441p:3
=198p+147p=345p
![](https://rs.olm.vn/images/avt/0.png?1311)
A = ( 6 : 3/5 - 7/6 * 6/7 ) : ( 21/5 * 10/11 + 57/11 )
A = ( 10 - 1 ) : ( 42/11 + 57/11)
A = 9 : 9
A = 1
B = 59 /10 : 3/2 - ( 7/3 * 9/2 - 2 * 7/3 ) : 7/4
B = 59/15 - ( 21/2 - 14/3 ) : 7/4
B = 59/15 - 35/6 : 7/4
B = 59/15 - 10/3
B = 3/5
![](https://rs.olm.vn/images/avt/0.png?1311)
A = ( 6 : 3/5 - 7/6 x 6/7 ) : ( 21/58 x 10/11 + 57/11 )
A = 9 : .....
A = .......
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(6\div\dfrac{3}{5}-1\dfrac{1}{6}\times\dfrac{6}{7}\right)\div\left(4\dfrac{1}{5}\times\dfrac{10}{11}+5\dfrac{2}{11}\right)\)
\(=\left(6\times\dfrac{5}{3}-\dfrac{7}{6}\times\dfrac{6}{7}\right)\div\left(\dfrac{21}{5}\times\dfrac{10}{11}+\dfrac{57}{11}\right)\)
\(=\left(10-1\right)\div\left(\dfrac{210}{55}+\dfrac{57}{11}\right)\)
\(=9\div9\)
\(=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\dfrac{4}{5}+\dfrac{7}{10}=\dfrac{8}{10}+\dfrac{7}{10}=\dfrac{15}{10}=\dfrac{3}{2}\\ b,\dfrac{7}{8}\times3+\dfrac{5}{12}=\dfrac{21}{8}+\dfrac{5}{12}=\dfrac{21\times3+5\times2}{24}=\dfrac{73}{24}\\ c,\dfrac{6}{9}:\left(\dfrac{2}{3}:3\right)=\dfrac{2}{3}:\dfrac{2}{3}\times3=1\times3=3\)
làm nhanh cho 1 kike 5 người nha
\(\left(\dfrac{7}{3}-\dfrac{7}{6}\right)\times\dfrac{2}{7}=\dfrac{7}{3}\times\dfrac{2}{7}-\dfrac{7}{6}\times\dfrac{2}{7}=\dfrac{2}{3}-\dfrac{2}{6}=\dfrac{2\times2-2}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)