7/12+9/20+11/30+17/72简便计算

7/12 + 9/20 + 11/30 + 17/72
= (6 + 1)/12 + 17/72 + (10 - 1)/20 + 11/30
= 1/2 + 6/72 + 17/72 + 1/2 - 3/60 + 22/60
= 1 + 23/72 + 19/60
= 1 + (24 - 1)/72 + (20 - 1)/60
= 1 + 1/3 - 1/72 + 1/3 - 1/60
= 1 + 2/3 - 5/360 - 6/360
= 1 + 240/360 - 11/360
= 1 + 229/360