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100 : y - 28 : y = 8
= ( 100 - 28 ) : y = 8
72 : y = 8
y = 72 : 8
y = 9
Câu 1:Tính hợp lí
a) 28.72+28.28
=28.(72+28)
=28.100
= 2800
b)50.5.2
=50.2.5
=100.5
= 500
Câu 2:Tìm x
a) 3x+6=15
3x =15-6
3x = 9
x = 9:3
x = 3
b)100-(4x+8):10=8
100-(4x+8) =8.10
100-(4x+8) = 80
4x+8 = 100-80
4x+8 = 20
4x = 20-8
4x = 12
x = 12:4
x = 3
K cho mk nhé!!!!!Thanks>_<
câu 1
a )
28x72+28x28
=28+72
=100
b )
50x5x2
=50x10
=500
câu 2
a )
3x+6=15
3x=15-6
3x=9
x=9:3
x=3
b)
100-(4x+8):10=8
100-(4x+8=)8x10
100-(4x+8)=80
4x+8=100-80
4x+8=20
4x=20-8
4x=12
x=12:4
x=3
c ) 815 - 23 - 77 + 185
= ( 815 + 185 ) - ( 23 + 77 )
= 1000 - 100 = 900
m ) 8 x 427 x 3 + 6 x 573 x 4
= 24 x 427 + 24 x 573
= 24 x ( 427 + 573 )
= 24 x 1000
= 24000
g ) 52 - 42 + 37 + 28 - 38 + 63
= ( 52 + 28 ) - ( 42 + 38 ) + ( 37 + 63 )
= 80 - 80 + 100
= 0 + 100
= 100
h ) 35 x 18 - 9 x 70 + 100
= 7 x 5 x 9 x 2 - 9 x 7 x 5 x 2 + 100
= 0 + 100
= 100
n ) 2008 x 867 + 2009 x 133
= 2008 x 867 + ( 2008 + 1 ) x 133
= 2008 x 867 + 2008 x 133 + 133
= 2008 x ( 867 + 133 ) + 133
= 2008 x 1000 + 133
= 2008000 + 133
= 2008133
i ) 326 x 78 + 327 x 22
= 326 x 78 + ( 326 + 1 ) x 22
= 326 x 78 + 326 x 22 + 22
= 326 x ( 78 + 22 ) + 22
= 326 x 100 + 22
= 32600 +22
= 32622
q ) ( 20 + 21 + 22 + 23 + 24 + 25 ) x ( 16 - 2 x 8 )
= ( 20 + 21 + 22 + 23 + 24 + 25 ) x ( 16 - 16)
= ( 20 + 21 + 22 + 23 + 24 + 25 ) x 0
= 0
\(32\times25+18\times100-50\times12\)
\(=800+1800-600\)
\(=2000\)
\(56\times45+28\times98+56\times6\)
\(=2520+2744+336\)
\(=5600\)
32 x 25 + 18 x 100 - 50 x 12 = 32 x 25 + 18 x 4 x 25 - 25 x 2 x 12
= 32 x 25 + 72 x 25 - 25 x 24
= ( 32 + 72 - 24 ) x 25
= 80 x 25
= 2000
56 x 45 + 28 x 98 + 56 x 6 = 56 x 45 + 28 x 2 x 49 + 56 x 6
= 56 x 45 + 56 x 49 + 56 x 6
= 56 x ( 45 + 49 + 6 )
= 56 x 100
= 5600
\(\left(72.72+72.28\right)+x:8\)
\(\left[72.\left(72+28\right)\right]+x:8\)
\(\left(72.100\right)+x:8\)
\(7200+x:8\)
\(x:8=-7200\)
\(x=-57600\)
vậy \(x=-57600\)
a. <=> 42 : x = 3
<=> x = 14
b. 25 * x = 15675
<=> x = 627
c. x = 19
b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16
= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8
= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)
= 1 + 1 + 7/4
= 2 + 7/4 = 15/4
c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16
= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2
= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2
= 14/7 + 12/6 + 5/8 + 1/2
= 2 + 2 + 5/8 + 1/2
= 4 + 9/8 = 41/8
100 : x - 28 : x = 8
(100-28):y=8
72:y=8
y=72:8
y=9
(100-28):x=8
72:x=8
x=9