Tính
A,9/15:17/15+8/5:17/15
B,100%+28,4%-36,7%
C,25:5/11
D,8/7:4
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25 tháng 7 2021
a) Ta có: \(\dfrac{9}{5}:\dfrac{17}{5}+\dfrac{8}{5}:\dfrac{17}{15}\)
\(=\dfrac{9}{5}\cdot\dfrac{5}{17}+\dfrac{8}{5}\cdot\dfrac{15}{17}\)
\(=\dfrac{9}{17}+\dfrac{24}{17}=\dfrac{33}{17}\)
5 tháng 4 2021
Bài 1:
Ta có: \(x-35\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow65\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow x=\dfrac{1}{25}:\dfrac{13}{20}=\dfrac{1}{25}\cdot\dfrac{20}{13}=\dfrac{4}{65}\)
Vậy: \(x=\dfrac{4}{65}\)
5 tháng 4 2021
Bài 2:
a) Ta có: \(17\dfrac{2}{31}-\left(\dfrac{15}{17}+6\dfrac{2}{31}\right)\)
\(=17\dfrac{2}{31}-\dfrac{15}{17}-6\dfrac{2}{31}\)
\(=11+\dfrac{2}{31}-\dfrac{15}{17}\)
\(=\dfrac{5366}{527}\)
9 tháng 8 2016
a) 3/7 + 4/9 + 4/7 + 5/9
= ( 3/7 + 4/7 ) + ( 4/9 + 5/9 )
= 7/7 + 9/9
= 1 + 1
= 2
b)1/5 + 4/10 + 9/15 + 16/20 + 25/25 + 36/30 + 49/35 + 64/40 + 81/45
= 1/5 + 2/5 + 3/5 + 4/5 + 5/5 + 6/5 + 7/5 + 8/5 + 9/5
= ( 1/5 + 9/5 ) + ( 2/5 + 8/5 ) + (7/5 + 3/5 ) + ( 4/5 + 6/5 ) + 5/5
= 2 + 2 + 2 + 2 + 1
= 2 x 4 + 1
= 8 +1
= 9
c) 1/8 + 1/12 + 3/8 + 5/12
= ( 1/8 + 3/8 ) + ( 1/12 + 5/12)
= 4/8 + 6/12
= 1/2 + 1/2
= 2/4 = 1/2
mỏi tay rồi
2 tháng 7 2021
1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)
\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)
=0
2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)
\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)
\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)
3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)
\(=\dfrac{52546}{15}\)
4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
18 tháng 7 2017
Bài 3:
a) 11 - (15 + 11) = x - (25 - 9)
=> 11 - 15 - 11 = x - 25 + 9
=> x = 9 - 25 + 15
=> x = -1
b) 2 - x = 17 - (-5)
=> 2 - x = 17 + 5
=> -x = 17 + 5 - 2
=> -x = 20
=> x = -20
c) x - 12 = (-9) - 15
=> x - 12 = -9 - 15
=> x = -9 - 15 + 12
=> x = -12
d) IxI - 7 = 9
=> IxI = 9 + 7
=> IxI = 16
=> x = 16 hay x = -16
e) 9 - 25 = (7 - x) - (25 + 7)
=> 9 - 25 = 7 - x - 25 - 7
=> x = 7 - 7 - 25 + 25 - 9
=> x = -9
Bài 4:
a) 25 . 46 + 54 . 25
= 25(46 + 54)
= 25.100
= 2500
b) 1200 : 25
= (25.48) : 25
= 25:25 . 48
= 1.48
= 48
c) 1356 - 998
= 1356 + 2 - 998 - 2
= 1358 - 1000
= 358
d) 117 + 57 - 17
= 117 - 17 + 57
= 100 + 57
= 157
Bài 5:
a) 34 . 315
= 34 + 15
= 319
b) 88 : 88
= 88 - 8
= 80
= 1
c) 100 - [120 - (15 - 5)2 ]
= 100 - (120 - 102)
= 100 - (120 - 100)
= 100 - 120 + 100
= 80
18 tháng 7 2017
Bài 3 :
a, 11 - ( 15 + 11 ) = x - ( 25 - 9 )
11 - 26 = x - 16
- 15 = x - 16
x = - 15 + 16
x = 1
b, 2 - x = 17 - ( - 5 )
2 - x = 22
x = 2 - 22
x = - 20
c, x - 12 = - 9 - 15
x - 12 = - 24
x = - 24 + 12
x = - 12
d, | x | - 7 = 9
| x | = 9 + 7
| x | = 16
x = 16 hoặc - 16
e, 9 - 25 = ( 7 - x ) - ( 25 + 7 )
- 16 = 7 - x - 32
x = 7 - 32 + 16
x = - 9
Bài 4 :
25 x 46 + 54 x 25
= 25 x ( 46 + 54 )
= 25 x 100
= 2500
b, 1200 : 25
= 12 x 100 : 25
= 12 x 4
= 48
c, 1356 - 998
= 358
d, 117 + 57 - 17
= ( 117 - 17 ) + 57
= 100 + 57
= 157
Bài 5 :
a, 3^4 . 3^15
= 3^19
b, 8^8 : 8^8
= 1
c, 100 - [ 120 - ( 15 - 5 )^2 ]
= 100 - ( 120 - 100 )
= 100 - 20 = 80
18 tháng 7 2017
bai 4 : a) = 2500
b)=48
c)=157
bai 5 : a)= 1162261467
b)=1
c)= 80
18 tháng 6 2023
a: =-1+17/20=-3/20
b: =(28/60-33/60)*(-25/3)
=(-1/12)*(-25/3)=1/12*25/3=25/36
c: \(=\dfrac{1}{3}\cdot\dfrac{1}{3}=\dfrac{1}{9}\)
A. 9/15 : 7/5 + 8/5 : 17/5 B. 100% + 28,4% - 36,7%
= ( 9/15 + 8/5 ) : 7/5 = 128,4% - 36,7%
= 33/15 : 7/5 = 91,7%
= 11/7
C. 25 : 5/11 = 55 D. 8/7 : 4 = 2/7
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