怎样简便就怎样算①0.25×1.25×0.8×0.4②[(25%-112)×316]÷0.375③1990×198.9-1989×198.8④2007÷200720072008+12009⑤(1+19105)+(1+19105×2)+(1+19105×3)+…(1+19105×20)-数学

题文

怎样简便就怎样算
①0.25×1.25×0.8×0.4
②[(25%-
1
12
3
16
]÷0.375
③1990×198.9-1989×198.8
④2007÷2007
2007
2008
+
1
2009

⑤(1+
19
105
)+(1+
19
105
×2)+(1+
19
105
×3)+…(1+
19
105
×20)
题型:解答题  难度:中档

答案


①0.25×1.25×0.8×0.4,
=(0.25×0.4)×(1.25×0.8),
=0.1×1,
=0.1;

②[(25%-
1
12
3
16
]÷0.375,
=[
1
6
×
3
16
]÷0.375,
=
1
32
÷0.375,
=
1
12


③1990×198.9-1989×198.8,
=1990×198.9-198.9×1988,
=×198.9,
=2×198.9,
=397.8;

④2007÷2007
2007
2008
+
1
2009

=2007÷
2007×2008+2007
2008
+
1
2009

=2007÷
2007×(2008+1)
2008
+
1
2009

=2007÷
2007×2009
2008
+
1
2009

=2007×
2008
2007×2009
+
1
2009

=
2008
2009
+
1
2009

=1;

⑤(1+
19
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