问题描述: 1/12+1/20+1/30+1/42=?简便计算, 1个回答 分类:数学 2014-11-12 问题解答: 我来补答 1/12+1/20+1/30+1/42=(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)=1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7=1/3-(1/4-1/4)-(1/5-1/5)-(1/6-1/6)-1/7=1/3-1/7=4/21 展开全文阅读