7/12+9/20+11/30+17/72简便计算速求

7/12+9/20+11/30+17/72简便计算
解，得：
==(42/72)*(17/72)+[(27/60)+(22/60)]
==(59/72)+(53/60)
==(3540/4320)+(3816/4320)
==7356/4320

这个……，应该没什么简便算法，只能是傻算！


7/12+9/20+11/30+17/72
=7/12+17/72+9/20+11/30
=(42/72+17/72)+(27/60+22/60)
=59/72+49/60
=(1/12)(59/6+49/5)
=(1/12)[(295+294)/30]
=(1/12)(589/30)
=589/360

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

7/12+9/20+11/30+17/72
=1/3+1/4+1/4+1/5+1/5+1/6+17/72
=（1/3+1/4+1/4+1/6）+（1/5+1/5+17/72）
=1+229/360
=1又229/360
这题目是不是有点问题？方法就是这样了。