42/15+102/35+186/63+294/99+426/143用简算

问题描述:

42/15+102/35+186/63+294/99+426/143用简算

=21*(1/3-1/5)+51*(1/5-1/7)+93*(1/7-1/9)+147*(1/9-1/11)+213*(1/11-1/13)
=7+6+6+6+6-213/13
=190/13