設(shè)大馬、中馬、小馬各為：
x+y+z=100 .(1)
3x+2y+1/2z=100,即6x+4y+z=200 .(2)
(2)-(1)：5x+3y=100
3y=100-5x=5(20-x)
y必須是5的倍數(shù),20-x必須是3的倍數(shù)
(1)*4-(2)：-2x+3z=200
z=2(x+100)/3
20-x可能等于3,6,9,12,15,18
20-x=3時x=17,y=5,z=78
20-x=6時x=14,y=10,z=76
20-x=9時x=11,y=15,z=74
20-x=12時x=8,y=20,z=72
20-x=15時x=5,y=25,z=70
20-x=18時x=2,y=30,z=68