560-557+554-551+……+500-497
问题描述：
560-557+554-551+……+500-497
答
11个3相加
答
(560-557)+(554-551)+……+(500-497)
规律：每两个一组,被减数和减数每次减少6,差不变都=3
一共有60/6+1=11组.
560-557+554-551+……+500-497
=3*11
=33