Question

观察下列等式1x2分之1=1-2分之1,2x3分之1=3分之1-4分之1将上面三个等式分别相加得：

Answer 1

1/1×2+1/2×3+1/3×4

=1/1-1/2+1/2-1/3+1/3-1/4

=1-1/4

=3/4