2分之1+3分之1+4分之3+5分之2+8分之7+20分之9+10分之21+24分之11+35分之19简便计算,

1/2+1/3+3/4+2/5+7/8+9/20+21/10+11/24+19/35
=(1/2+1/3)+(3/4+2/5)+9/20+21/10+(7/8+11/24)+19/35
=5/6+(23/20+9/20+21/10)+32/24+19/35
=5/6+74/20+8/6+19/35
=13/6+37/10+19/35
=(13*5+37*3)/30+19/35
=176/30+19/35
=(176*7+19*6)/210
=(1232+114)/210
=1346/210
=673/105