Question

一乘二分之一加上二乘三分之一加上三乘四分之一一直加到四十九乘五十分之一等于几 终身大事啊

Answer 1

1/(1×2)+1/(2×3)+1/(3×4)+……1/(49×50)

=1/1-1/2+1/2-1/3+1/3-1/4+……+1/49-1/50

=1-1/50

=49/50