Tính bằng cách thuận tiện nhất:
a, 3/5 + 7/12 + 5/12
b, 4/26 + 2/5 x 26
c, 5/7 x 9/16 + 7/16 x 5/7
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60x [7/12+4/15]
60x153/180
=9180/180
b 1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9=40320/4032
a: =8/15x1/4=2/15
b: \(=\dfrac{5}{3}\cdot\dfrac{4}{5}\cdot\dfrac{6}{7}=\dfrac{24}{21}=\dfrac{8}{7}\)
c: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)
`39/16 : 5/8 - 7/16 : 5/8`
`=39/16 xx 8/5- 7/16 xx 8/5`
`=8/5 xx (39/16 - 7/16)`
`= 8/5 xx2`
`= 16/5`
__
` 4/3 xx 9/8 - 4/3 xx 3/8`
`=4/3 -(9/8 - 3/8)`
`= 4/3 xx 3/4`
`=1`
\(a,\\ \dfrac{39}{16}:\dfrac{5}{8}-\dfrac{7}{16}:\dfrac{5}{8}\\ =\dfrac{39}{16}\cdot\dfrac{8}{5}-\dfrac{7}{16}\cdot\dfrac{8}{5}\\ =\dfrac{8}{5}\cdot\left(\dfrac{39}{16}-\dfrac{7}{16}\right)=\dfrac{8}{5}\cdot2=\dfrac{16}{5}\\ b,\\ \dfrac{4}{3}\cdot\dfrac{9}{8}-\dfrac{4}{3}\cdot\dfrac{3}{8}=\dfrac{3}{2}-\dfrac{1}{2}=1\)
a: =428(36+64)=42800
b: =512(47-37)=5120
c: =72x100=7200
a) 4 x 78 x 5
= (4 x 5) x 78
= 20 x 78
= 1560
b) 2 x 99 x 5
= (2 x 5) x 99
= 10 x 99
= 990
1.a,=(54+45+1).113
=100.113
=11300
b,=(3/7+8/14)+(4/9+10/18)
=1+1
=2
2.a,=13/10+1/3
=49/30
b,=12/9.(1/12+1/6)
=12/9.1/4
=1/3
c,=3/4.3/2
=9/8
d,=3/2-1/3
=7/6
1:tính bằng cách thuận tiện nhất:
a)54 x 113 + 45 x 113 + 113
= 54 x 113 + 45 x 113 + 113x1
=113 x(54+45+1)
= 113x100
=1300
b)3/7 + 4/9 + 8/14 + 10/18
=(3/7+8/14)+(4/9+10/18)
= 1 + 1
=2
\(a,=\left(\dfrac{3}{5}+\dfrac{3}{5}+\dfrac{6}{5}\right)\times\left(\dfrac{6}{7}:7\right)=3\times\dfrac{6}{49}=\dfrac{18}{49}\)
8/5
686/65
5/7
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