东海私募 春芽
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设(0.1+0.12+0.123+0.1234)=A,(0.12+0.123+0.1234)=B,则A-B=0.1,
(0.1+0.12+0.123+0.1234)×(0.12+0.123+0.1234+0.12345)-(0.1+0.12+0.123+0.1234+0.12345)×(0.12+0.123+0.1234)
=A×(B+0.12345)-(A+0.12345)×B
=AB+0.12345A-(AB+0.12345B)
=AB+0.12345A-AB-0.12345B
=0.12345×(A-B)
=0.12345×0.1
=0.012345.
点评:
本题考点: 小数的巧算.
考点点评: 对于此类问题,一般采取把某个算式用字母代替,然后把字母代入算式中,使运算简便.
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