2 1/6+4 1/12+6 1/20+8 1/30+10 1/42+12 1/56+14 1/72+16 1/90
问题描述:
2 1/6+4 1/12+6 1/20+8 1/30+10 1/42+12 1/56+14 1/72+16 1/90
答
2 又1/6+4又 1/12+6 又1/20+8又 1/30+10又 1/42+12又 1/56+14 又1/72+16又 1/90
=(2+4+6+8+10+12+14+16)+(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
=(2+16)×8÷2+(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
=72+(1/2-1/10)
=72+0.4
=72.4