由题意得；PQ：AD=BP：AB，PN：BC=AP：AB∴ PQ AD + PN BC = BP AB + AP AB = AP+PB AB = AB AB =1，又∵PN=2PQ，BC=8cm，AD=6cm，∴ PQ 6 + 2PQ 8 =1，∴PQ=2.4则PN=4.8，∴矩形PQMN的周长=14.4cm．
