小学数学分数超难简算题

分子=1-1/2+1/3-1/4+⋯+1/49-1/50
=(1+1/2+1/3+1/4+...+1/50)-2(1/2+1/4+1/6+...+1/50)
=1+1/2+1/3+1/4+...+1/50-1-1/2-1/3-...-1/25
=1/26+1/27+1/28+...+1/50=a
分母=1/52+1/54+1/56+⋯+1/100

=(1/2)(1/26+1/27+1/28+...1/50)=(a/2)
a/(a/2)=2
(1-1/2+1/3-1/4+⋯+1/49-1/50)/(1/52+1/54+1/56+⋯+1/100)
原式=2