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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.
\(\frac{12}{5}+\frac{1}{5}\times6-\frac{3}{4}\)
\(=2,4+0,2\times6-0,75\)
\(=2,4+1,2-0,75\)
\(=3,6-0,75=2,85\)
\(\frac{9}{7}-\frac{1}{7}\times3+\frac{15}{14}\)
\(=\frac{9}{7}-\frac{3}{7}+\frac{15}{14}\)
\(=\frac{18}{14}-\frac{6}{14}+\frac{15}{14}\)
\(=\frac{12}{14}+\frac{15}{14}\)
\(=\frac{27}{14}\)
\(a,\dfrac{4}{5}+\dfrac{7}{10}=\dfrac{8}{10}+\dfrac{7}{10}=\dfrac{15}{10}=\dfrac{3}{2}\\ b,\dfrac{7}{8}\times3+\dfrac{5}{12}=\dfrac{21}{8}+\dfrac{5}{12}=\dfrac{21\times3+5\times2}{24}=\dfrac{73}{24}\\ c,\dfrac{6}{9}:\left(\dfrac{2}{3}:3\right)=\dfrac{2}{3}:\dfrac{2}{3}\times3=1\times3=3\)
` a,`
`1/3 + 3/4 xx 5/9 `
`=1/3 + (3/4 xx 5/9) `
`= 1/3 + 5/12 `
`= 4/12 + 5/12`
`= 9/12 `
`= 3/4 .`
`b,`
` 7/12 - 5/4 xx 2/15 `
`= 7/12 - (5/4 xx 2/15)`
`= 7/12 - 1/6`
`= 7/12 - 2/12 `
`= 5/12 .`