2又1/5-11/30+13/42-15/56+17/72-19/90+21/110-23/132奥数简算,急!

2又1/5-11/30+13/42-15/56+17/72-19/90+21/110-23/132奥数简算,急!
2又1/5-11/30+13/42-15/56+17/72-19/90+21/110-23/132
奥数简算,急!

2又1/5-11/30+13/42-15/56+17/72-19/90+21/110-23/132奥数简算,急!
2又1/5-11/30+13/42-15/56+17/72-19/90+21/110-23/132
=2又1/5-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)+(1/8+1/9)-(1/9+1/10)+(1/10+1/11)-(1/11+1/12)
=2又1/5-1/5-1/12
=2-1/12
=1又11/12

很简单：原式=2+1/5-1/5-1/6+1/6+1/7-1/7-1/8+1/8+1/9-1/9-1/10+1/10+1/11-1/11-1/12=2-1/12=1又11/12