In five days, four black cows and three brown cows give as much milk, as five brown cows and three black cows would give in four days.

Which color cows are the best milk producers?

(In reply to

Puzzle Solution by K Sengupta)

B and R possess the same meaning as in the previous post. Let the amount consumed by 4 black cows and 3 brown cows in 5 days, which is equal to the amount consumed by 5 brown cows and 3 black cows in 4 days, be A(say).

Then, by the given conditions, we must have:

4B + 3R = A/5, and:

3B + 5R = A/4

Then, (8/11)*(4B + 3R) - (7/11)*(3B + 5R) = 8A/55 - 7A/44

Or, B - R = -3A/220

Or, R = B + 3A/220

Thus, the per day yield of each brown cow is greater than that of each black cow, and consequently, the brown color cows are the best milk producers.