4/5+49/5+499/5+4999/5+49999/5

问题描述:

4/5+49/5+499/5+4999/5+49999/5

每一项补上个1/5呗
原式=1+10+100+1000+10000-1/5-1/5-1/5-1/5-1/5
=11111-1
=11110