设竖式纸盒有a个,横式纸盒有b个,则共用长方形纸板(4a+3b)块,正方形纸板(a+2b)块.根据题意有:
(a+2b):(4a+3b)=2:5,
即5(a+2b)=2(4a+3b),
5a+10b=8a+6b,
3a=4b,
即a:b=4:3.