设空桶容量为X,则有X*2/5 = 30A;X*(1-2/5)*(1/2) = 10B;X-30A-10B = 30C;由第二式可得 30B = 10B*3 = X*9/10由第三式可得 30C = X-X*2/5-X*3/10 = X*3/10则得A:B:C = 30A : 30B : 30C = (2/5):(9/10):(3/10) = 4:9:3
设空桶y 30A=(2/5)y10B=(2/5)(1/2)y30c=y-(2/5)(1/2)yA/B/C=2/3/4