(1+19/78×1)+(1+19/78×2)+(1+19/78×3)+……+(1+19/78×12)=?
问题描述:
(1+19/78×1)+(1+19/78×2)+(1+19/78×3)+……+(1+19/78×12)=?
答
=12x1+19/78x(1+12)x12/2=12+19=31
(1+19/78×1)+(1+19/78×2)+(1+19/78×3)+……+(1+19/78×12)=?
=12x1+19/78x(1+12)x12/2=12+19=31