题目内容

2.05+5.71+0.95=5.71+（2.05+0.95）使用了（　　）

A．加法交换律

B．加法交换律和结合律

C．加法结合律

分析：在加法算式中，两个加数交换位置，和不变，此为加法交换律；先把前两个数相加，或先把后两个数相加，和不变，此为加法结合律．由此可知，2.05+5.71+0.95=5.71+（2.05+0.95）同时使用了加法交换律及结合律．

解答：解：根据加法交换律及结合律的定义可知，
2.05+5.71+0.95=5.71+（2.05+0.95）同时使用了加法交换律及结合律．
故选：B．

点评：同运用运算定律进行简算的时候，同一个算式可能要综合运用多个运算定律进行简算．

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