【问题】在学习了加法交换律和结合律后的一次练习中,“75+47+25、265-78-65、130-45+70”这三道题学生完成的情况让我十分的惊讶和不解,第一题全班。都能用交换律进行简便计算,而后两题只有极个别的学生进行了巧算。在我们看来极为简单的两道题,为什么学生没想到?是因为没有巧算的意识,还是其他什么原因?“第一题可以运用加法交换律进行简便计算,第 [Question] After studying the law of addition and exchange law and practice of a combination of law, ”75 +47 +25,265-78-65,130-45 +70 “ The three questions students completed I was very The surprised and puzzled, the first question the whole class. Can use the exchange law for easy calculation, and then only two very few students conducted a tricky calculation. Why is it that students did not think about it because they did not have the skill to calculate or what other reasons? ”The first question can be easily calculated using the addition exchange law. The first