3/14+5/7+1/21 11/9-7/18-2/3 (简便计算)

如题所述

方法一:
3/14+5/7+1/21
=9/42+30/42+2/42
=(9+2+30)/42
=41/42
11/9-7/18-2/3
=22/18-7/18-12/18
=(22-12-7)/18
=3/18
=1/6
(此方法思路简单,但运用简便方法不明显。)
方法二:
3/14+5/7+1/21
=(1/2-2/7)+5/7+(1/3-2/7)
=(1/2+1/3)+(5/7-2/7-2/7)
=5/6+1/7
=41/42
11/9-7/18-2/3
=(1+2/9)-(1/2-1/9)-(1-1/3)
=(1-1)+(2/9+1/9)+1/3-1/2
=0+1/3+1/3-1/2
=2/3-1/2
=1/6
(此方法思路复杂,但明显运用了简便方法。)
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