Question

1,27+2,77+4,27+5,77+7,27+8,77+10,27+11,77+13,27+14,77 

Answer 1

Đặt A=1,27+2,77+...+14,77

A có: (14,77-1,27)/1,5+1=10

A=(14,77+1,27)*10/2=80,2

Answer 2

401\5 nhé