题目
用简便方法计算各题分数的题
1/5+5/6+4/5 7/9-1/7-2/4 2/15+4/21+7/15+2/21 2/3-1/2+2/3-1/2
5/12+(1/12-2/5) 2/15+(2/5-1/15)-1/5
1/5+5/6+4/5 7/9-1/7-2/4 2/15+4/21+7/15+2/21 2/3-1/2+2/3-1/2
5/12+(1/12-2/5) 2/15+(2/5-1/15)-1/5
提问时间:2020-12-02
答案
用简便方法计算各题分数的题
1/5+5/6+4/5
=(1/5+4/5)+5/6
=1+5/6
=1又5/6
7/9-1/7-2/9
=(7/9-2/9)-1/7
=5/9-1/7
=25/63
2/15+4/21+7/15+2/21
=(2/15+7/15)+(4/21+2/21)
=3/5+2/7
=31/35
2/3-1/2+2/3-1/2
=(2/3+2/3)-(1/2+1/2)
=4/3-1
=1/3
5/12+(1/12-2/5)
=(5/12+1/12)-2/5
=1/2-2/5
=1/10
2/15+(2/5-1/15)-1/5
=(2/15-1/15)+(2/5-1/5)
=1/15+1/5
=4/15
1/5+5/6+4/5
=(1/5+4/5)+5/6
=1+5/6
=1又5/6
7/9-1/7-2/9
=(7/9-2/9)-1/7
=5/9-1/7
=25/63
2/15+4/21+7/15+2/21
=(2/15+7/15)+(4/21+2/21)
=3/5+2/7
=31/35
2/3-1/2+2/3-1/2
=(2/3+2/3)-(1/2+1/2)
=4/3-1
=1/3
5/12+(1/12-2/5)
=(5/12+1/12)-2/5
=1/2-2/5
=1/10
2/15+(2/5-1/15)-1/5
=(2/15-1/15)+(2/5-1/5)
=1/15+1/5
=4/15
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