你好:
1/3+3/4+2/5+5/7+7/8+9/20+10/21+11/24+12/35
=1/3+3/4+2/5+5/7+7/8+(5/20+4/20)+(3/21+7/21)+(3/24+8/24)+(5/35+7/35)
=1/3+3/4+2/5+5/7+7/8+1/4+1/5+1/7+1/3+1/8+1/3+1/7+1/5
=(1/3×3)+(3/4+1/4)+(2/5+1/5+1/5)+(5/7+1/7+1/7)+(7/8+1/8)
=1+1+4/5+1+1
=4又4/5
=4.8
1/3+3/4+2/5+5/7+7/8+9/20+10/21+11/24+12/35
=1/3+3/4+2/5+5/7+7/8+(5/20+4/20)+(3/21+7/21)+(3/24+8/24)+(5/35+7/35)
=1/3+3/4+2/5+5/7+7/8+1/4+1/5+1/7+1/3+1/8+1/3+1/7+1/5
=(1/3×3)+(3/4+1/4)+(2/5+1/5+1/5)+(5/7+1/7+1/7)+(7/8+1/8)
=1+1+4/5+1+1
=24/5
=4.8
24/5