+107 If a farmer can trade four chickens for a p*g, three pigs for two sheep, and five sheep for two cows, what is the minimum number of cows he needs to trade for 20 chickens?
+128474 Let
Chickens = x
Pigs = y
Sheep = z
Cows = w
So
4x = 1y ⇒ y = 4x
3y = 2z ⇒ 3(4x) = 2z ⇒ 12x = 2z ⇒ 6x = z
5z = 2w ⇒ 5(6x) = 2w ⇒ 30x = 2w ⇒ 15x = 1w
So
1w / 15x = ?w / 20x
1 / 15 = ? / 20
20 / 15 = ? = 4/3 cows for 20 chickens
+36916 4 b /p 3/2 p/s 5/2 s/c = 15 b/c (birds per cow)
20 b / 15 b/c = 1 1/3 c ~~~ He will need to trade 2 cows
