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3.用简单的方法计算下面各题.不能直接写得数.快急.

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3.用简单的方法计算下面各题.不能直接写得数.快急.
9/17+(5/12+8/17) 7/15-(4/15+2/25) 2/11+5/7+9/11
= = =
= = =
7/10+4/9+13/10+5/9
=
=
●9/17+(5/12+8/17)
=9/17+8/17+5/12
=17/17+5/12
=1+5/12
=1又5/12
●7/15-(4/15+2/25)
=7/15-4/15-2/25
=3/15-2/25
=15/75-6/75
=9/75
=3/25
●2/11+5/7+9/11
= 2/11+9/11+5/7
=11/11+5/7
=1+5/7
=1 又5/7
●7/10+4/9+13/10+5/9
=(7/10+13/10)+(4/9+5/9)
=20/10+9/9
=2+1
=3
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