一條F.1數學

Let X = 雞
Let Y = 兔

X + Y = 35 (一共有35隻)

2X + ((2/3 Y) x 4) + ((1/3 Y) x 3) = 90 (兩隻腳的雞 + 4隻腳的正常兔 + 3隻腳的不正常兔 共有90隻腳)

(70 - 2Y) + 8Y/3 + 3Y/3 = 90

(210 - 6Y)/3 + 8Y/3 + 3Y/3 = 90

210 - 6Y + 8Y + 3Y = 270

5Y = 60

Y=12

所以 X = 23 (雞)
正常兔 = 12 x 2/3 = 8 (正常兔)

let x be no. of chicken
y be no. of 4-leg rabbits
z be no, of 3-leg rabbits


x+y+z = 35 (1)
2x+4y+3z = 90 (2)
z = (y+z) / 3 (3)

from (3)
z = y/3 + z/3
2z/3 = y/3
z = y/2

put z = y/2 into (1)
x+y+y/2 = 35
x+3y/2 = 35
x = 35-3y/2

put x = 35-3y/2 into (2)
2(35-3y/2)+4y+3(y/2) = 90
70-3y+4y+3y/2 = 90
2.5y = 20
y = 8

z = 4

x = 23

雞 : 23
四腳兔 : 8