题目内容

(1)在知识竞赛中，如果＋10表示加10，那么扣20分怎样表示？

(2)某人转动转盘，如果用＋5表示沿用逆时针方向转了5圈，那么沿顺时针方向转了12圈怎样表示？

(3)在某次乒乓球质量检测中，一只乒乓球超出标准质量0.02克记作＋0.02，那么－0.03克表示什么？

答案：
解析：

　　解：(1)扣20分记作－20分；

　　(2)顺时针方向转了12圈记作－12圈；

　　(3)－0.03克表示乒乓球的质量低于标准质量0.03克．

　　说明：通过三个实例说明如何用正负数表示这种具有相反意义的量．


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