20/1+30/1+42/1+56/1+72/1+90/1救简算

20/1+30/1+42/1+56/1+72/1+90/1救简算 1/30+1/42+1/56+1/72+1/90 1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 1/12+1/20+1/30+1/42+1/56+1/72+1/90 20/1+30/1+42/1+56/1+72/1+90/1 用简便方法计算. 1/20+1/30+1/42+1/56+1/72+1/90 算1/20+1/30+1/42+1/56+1/72+1/90 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+.1/9900 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/10 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 谁能巧算1-1/2-1/6-1/12-1/20-1/30-1/42-1/56-1/72-1/90 1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 急!