math
posted by Anna .
On the plant ZOG,colored coins are used formoney. Suppose 12 white, 9 red, 8 yellow, 4 blue, and 0 green can be exchanged for 2 white, 1 red, 0 yellow, 1 blue ,and 1 green. Also, suppose 1 green = N blue, 1 blue = N yellow, 1 yellow = N red, and 1 red = N white coins. What is the rate of exchange for these coins?

From your first condition
12w+9r+8y+4b = 2w+1r+1b+1g
so 10w+8r+8y+3bg = 0
from your last conditions, w is the smallest denomination and g is the largest, so that
r=Nw
y=N^2w
b=N^3w and
g = N^4w
putting those back in
10w + 8Nw + 8n^2w + 3N^3w  N^4w = 0
divide by w
10 + 8N + 8N^2 + 3N^3  N^4 = 0
Hoping that N is a whole number, I only had to try N = 1,2, or 5 (factors of 10)
sure enough N=5 worked, so
smallest coin W
1 R = 5 W
1 Y = 25 W
1 B = 125 W and
1 G = 625 W