空的那几题,急急急急
2014-09-10
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88×17/87
=(87+1)×17/87
=87×17/87+1×17/87
=17又17/87
3/10+99×3/10
=3/10×(99+1)
=3/10×100
=30
7/13×5/9+5/9×7/13
=7/13×(5/9+5/9)
=7/13×10/9
=70/117
=(87+1)×17/87
=87×17/87+1×17/87
=17又17/87
3/10+99×3/10
=3/10×(99+1)
=3/10×100
=30
7/13×5/9+5/9×7/13
=7/13×(5/9+5/9)
=7/13×10/9
=70/117
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