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a. 2/5 + 3/7 + 3/5 + 4/7
= (2/5 + 3/5) + (3/7 + 4/7)
= 1 + 1 = 2
b. 2/3 x 4/9 + 2/3 x 5/9
= 2/3 x (4/9 + 5/9)
= 2/3 x 1 = 2/3
a: =428(36+64)=42800
b: =512(47-37)=5120
c: =72x100=7200
6/x = 4/6 ; 6/x giữ nguyên 4/6 = 2/3 = 6/9 => x= 9
x/72 = 10/16 ; 10/16 = 5/8 = 45/72 => x = 45
x + 1/6 = 2/3 x = 2/3 - 1/6 = 1/2 => x = 1/2
x - 2/12 = 3/4 x = 3/4 + 2/12 = 11/12
72 : 3 x x = 4
=> 24 x x = 4
=> x = 4:24
=> x = 1/6
Vậy \(x=\frac{1}{6}\)
1: \(=\dfrac{1}{3}\cdot\dfrac{3}{7}\cdot\dfrac{1}{2}=\dfrac{1}{7\cdot2}=\dfrac{1}{14}\)
2: =5/12+1/7
=35/84+12/84=47/84
3: =8(8/9-6/9)
=8*2/9=16/9
4: \(=\dfrac{5}{12}\cdot\dfrac{12}{5}=1\)
5: =16/5+6
=16/5+30/5=46/5
6: =10*1/2-10*1/5
=5-2=3
\(a,C1:\left(524-168\right):4=356:4=89\\ C2:\left(524-168\right):4=524:4-168:4=131-42=89\)
\(b,C1:72:\left(9\times4\right)=72:36=2\\C2:72:\left(9\times4\right)=\left(72:9\right):4 =8:4=2\)
\(c,C1:\left(25\times72\right):9=1800:9=200\\ C2:\left(25\times72\right):9=25\times\left(72:9\right)=25\times8=200\)
a,C1:(524−168):4=356:4=89C2:(524−168):4=524:4−168:4=131−42=89a,C1:(524−168):4=356:4=89C2:(524−168):4=524:4−168:4=131−42=89
b,C1:72:(9×4)=72:36=2C2:72:(9×4)=(72:9):4=8:4=2b,C1:72:(9×4)=72:36=2C2:72:(9×4)=(72:9):4=8:4=2
c,C1:(25×72):9=1800:9=200C2:(25×72):9=25×(72:9)=25×8=200
X bằng 6