Question

1/2020加2/2020一直加到2019/2020怎么算？

Answer 1

1+2+3+...+2019
=(1+2019)x2019/2
=2020x2019/2
//
1/2020+2/2020+...+2019/2020
=(1+2+...+2019)/2020
=[2020x2019/2]/2020
=2019/2