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Bài 2:
a, \(\dfrac{5}{23}\) \(\times\) \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) \(\times\) \(\dfrac{9}{26}\)
= \(\dfrac{5}{23}\) \(\times\) ( \(\dfrac{17}{26}\) + \(\dfrac{9}{26}\))
= \(\dfrac{5}{23}\) \(\times\) \(\dfrac{26}{26}\)
= \(\dfrac{5}{23}\)
b, \(\dfrac{3}{4}\) \(\times\) \(\dfrac{7}{9}\) + \(\dfrac{7}{4}\) \(\times\) \(\dfrac{3}{9}\)
= \(\dfrac{7}{12}\) + \(\dfrac{7}{12}\)
= \(\dfrac{14}{12}\)
= \(\dfrac{7}{6}\)
a) (x + 73) - 26 = 76
x + 73 = 76 + 26
x + 73 = 102
x = 102-73
x = 29
b) 45-(c + 9) = 6
c + 9 = 6 + 45
c + 9 =51
c =51 - 9
c = 42
c) 89 - (73 - x)= 20
73 - x = 89 - 20
73 - x = 69
x = 73 - 69
x = 4
d) (x + 7) - 25 = 13
x + 7 = 13 + 25
x + 7 = 38
x = 38 - 7
x = 31
e) 198 - (x + 4) = 120
x + 4 = 198 - 120
x + 4 = 68
x = 68 - 4
x = 64
Bài 4
35/85 = 7/17
36/108 = 1/3
25/100 = 1/4
39/52 = 3/4
Bài 8
a) 9/8 và 7/12
= 8×3=24 ; 12×2=24
=>9/8 =27/24
=> 7/12 ; 14/24
b) 3/20 và 4/15
=20×3=60 ; 15×4=60
=> 9/60 ; 16/60
Bài 9
a) \(\frac{3}{8},\frac{15}{8},\frac{9}{8},\frac{7}{8}\)
Từ lớn -> bé:
=>\(\frac{15}{8},\frac{9}{8},\frac{7}{8},\frac{3}{8}\)
b) \(\frac{4}{15},\frac{3}{5},\frac{8}{45},\frac{7}{15}=\frac{12}{45},\frac{27}{45},\frac{8}{45},\frac{21}{45}\)
Từ lớn -> bé:
=> \(\frac{3}{5},\frac{7}{15},\frac{4}{15},\frac{8}{45}\)
c) \(\frac{3}{8},\frac{4}{5},\frac{47}{40},\frac{9}{4}=\frac{15}{40},\frac{32}{40},\frac{47}{40},\frac{90}{40}\)
Từ lớn -> bé:
=>\(\frac{9}{4},\frac{47}{40},\frac{4}{5},\frac{3}{8}\)
Bài 10
a, Ta có
`x/15 < 4/15`
` <=> x < 4`
` <=> x ∈ {1 ; 2 ; 3}`
b, Ta có
`5/9 > x/9`
` <=> 5 > x`
` <=> x ∈ {1 ; 2 ; 3 ; 4}`
c, Ta có
`1 <x/8 < 11/8`
` <=> 8/8 < x/8 < 11/8`
` <=> 8 < x <11`
` <=> x ∈ {9 ; 10}`
a;
c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
Bài 1:
a; (\(\dfrac{1}{4}\)\(x\) - \(\dfrac{1}{8}\)) x \(\dfrac{3}{4}\) = \(\dfrac{1}{4}\)
\(\dfrac{1}{4}x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{4}\) : \(\dfrac{3}{4}\)
\(\dfrac{1}{4}\)\(x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{4}\) x \(\dfrac{4}{3}\)
\(\dfrac{1}{4}x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{3}\)
\(\dfrac{1}{4}x\) = \(\dfrac{1}{3}\) + \(\dfrac{1}{8}\)
\(\dfrac{1}{4}\) \(x\)= \(\dfrac{8}{24}\) + \(\dfrac{11}{24}\)
\(\dfrac{1}{4}x=\dfrac{11}{24}\)
\(x=\dfrac{11}{24}:\dfrac{1}{4}\)
\(x=\dfrac{11}{24}\times4\)
\(x=\dfrac{11}{6}\)
b; \(\dfrac{12}{5}:x\) = \(\dfrac{14}{3}\) x \(\dfrac{4}{7}\)
\(\dfrac{12}{5}\) : \(x\) = \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{12}{5}\) : \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{12}{5}\) x \(\dfrac{3}{8}\)
\(x\) = \(\dfrac{9}{10}\)
2. i) 13.x + 15.x + 12.x = 120
=> (13 + 15 + 12).x = 120
=> 40.x = 120
=> x = 120 : 40
=> x = 3
k) 63 + 83 . 9 = (x + 120): x + 209
=> 63 + 747 - 209 = 1 + 120 : x
=> 120 : x + 1 = 601
=> 120 : x = 601 - 1
=> 120 : x = 600
=> x = 120 : 600
=> 1/2
k) 375 - 75.(x - 75) = 300
=> 75.(x - 75) = 375 - 300
=> 75.(x - 75) = 75
=> x - 75 = 1
=> x = 75 + 1
=> x = 76
Bài 2 :
a ) x + 23 = 100 : 2,5
x + 23 = 40
x = 40 - 23
x = 17
Vậy x = 17
b ) 8,4 + 1,6 * x = 7,4 + 2,6
8,4 + 1,6 * x = 10
1,6 * x = 10 - 8,4
1,6 * x = 1,6
x = 1,6 : 1,6
x = 1
Vậy x = 1
c ) ( x - 375 ) : 23 + 35 = 86
( x - 375 ) : 23 = 86 - 35
( x - 375 ) : 23 = 51
x - 375 = 51 * 23
x - 375 = 1173
x = 1173 + 375
x = 1548
Vậy x = 1548
d ) 375 - ( 113 - x ) * 3 = 168
( 113 - x ) * 3 = 375 - 168
( 113 - x ) * 3 = 207
113 - x = 207 : 3
113 - x = 69
x = 113 - 69
x = 44
Vậy x = 44
e ) 2013 - ( x - 1 ) * 13 = 2000
( x - 1 ) * 13 = 2013 - 2000
( x - 1 ) * 13 = 13
x - 1 = 13 : 13
x - 1 = 1
x = 1 + 1
x = 2
Vậy x = 2
g ) x : 7 + 20 = 17 * 49 + 17 * 51
x : 7 + 20 = 17 * ( 49 + 51 )
x : 7 + 20 = 17 * 100
x : 7 + 20 = 1700
x : 7 = 1700 - 20
x : 7 = 1680
x = 1680 * 7
x = 11760
Vậy x = 11760
f ) 987 - ( x + 189 ) : 3 = 537
( x + 189 ) : 3 = 987 - 537
( x + 189 ) : 3 = 450
x + 189 = 450 * 3
x + 189 = 1350
x = 1350 - 189
x = 1161
Vậy x = 1161
Các phần còn lại tương tự
bài2 \(x\times\dfrac{15}{16}-x\times\dfrac{4}{16}=2\)
\(x\times\dfrac{11}{16}=2\)
\(x=2:\dfrac{11}{16}\)
\(x=\dfrac{32}{11}\)
Bài 1 :
\(\dfrac{x}{16}\times\left(2017-1\right)=2\)
\(\dfrac{x}{16}\times2016=2\)
\(\dfrac{x}{16}=\dfrac{2}{2016}\)
\(x=\dfrac{2}{2016}\times16\)
\(x=\dfrac{1}{63}\)
a. 71-(33+x)=26
b. (x+73)-26=76
c. 45-(x+9)=6
d. 89-(73-x)=20
e. (x+7)-25=13
f. 198-(x+4)=120
g. 140:(x-8)=7
h. 4(x+41)=400
i. 11(x-9)=77
j. 5(x-9)=350
k. 2x-49=5 .3 mũ 2
l.200-(2x+6)=4 mũ 3
BÀI LÀM:
x+9=-31
x=-31-9
x=-40