parallelogram

圖片參考：http://img534.imageshack.us/img534/4958/0005wf.jpg




△ACE
= 2/(2+3) * △ACD
= 2/(2+3) * 1/2 * ABCD
= (1/5) ABCD

△AEF
= AF/(AF + FD) * △AED
= AB/(AB + ED) * △AED
= (2+3)/(2+3 + 3) * △AED
= 5/8 * △AED
= 5/8 * 3/(2+3) * △ACD
= 5/8 * 3/(2+3) * 1/2 * ABCD
= (3/16) ABCD

△DBF
= DF/(DF+FA) * △ABD
= ED/(ED+AB) * △ABD
= 3/(3+ 2+3) * △ABD
= 3/(3+ 2+3) * 1/2 * ABCD
= (3/16) ABCD

CEFA : △DBF
= (△ACE + △AEF) : △DBF
= (1/5 + 3/16) : (3/16)
= (16 + 3*5) : (3*5)
= 31 : 15

Answer is (C).