简便计算、急!2.9+29.9+299.9+299 - 知识问答

简便计算、急!2.9+29.9+299.9+2999.9、65X65/66、 12/7-（3/8+5/7）、65/66=

1个回答

2.9+29.9+299.9+2999.9
=(2.9+0.1)+(29.9+0.1)+(299.9+0.1)+(2999.9+0.1)-0.1*4
=3333-0.4
=3332.6
65*65/66
=65*(66-1)/66
=65-1/66
=64又65/66
=12/7-5/7-3/8
=5/8

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