S三:25乘以12除2=150(dm)
S平:16乘以25=400(dm)
S梯:【16+(16+12)】乘以25除以2=550(dm)
S平:S三 S梯:S三
=400:150 =550:150
=8:3 =11:3
(这样写绝对不会错)