1/2 × 1/5 + 1/5 × 1/8 + 1/8 × 1/11 + 1/11 × 1/14 + 1/14 × 1/17
问题描述:
1/2 × 1/5 + 1/5 × 1/8 + 1/8 × 1/11 + 1/11 × 1/14 + 1/14 × 1/17
答
=1/3×(1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17)
=1/3×(1/2-1/17)
=1/3×(15/34)
=5/34