1/1×4+1/4×7+1/7×10+...+1/97×100 =(1/3)×(3/1×4+3/4×7+3/7×10+...+3/97×100) =(1/3)×[(1-1/4)+(1/4-1/7)+(1/7-1/10)+...+(1/97-1/100)] =(1/3)×(1-1/4+1/4-1/7+1/7-1/10+...+1/97-1/100) =(1/3)×(1-1/1...