Milkman's Puzzle : Solution

Call one ten-gallon (40 quarts) milk can A and the other B, then proceed as follows:

	Can A	Can B	4 pail	5 pail
Initial position:	40	40	0	0
Fill 5 pail from can A.	35	40	0	5
Fill 4 pail from 5 pail, leaving 1 quart in 5 pail.	35	40	4	1
Empty 4 pail into can A.	39	40	0	1
Pour the quart from 5 pail into 4 pail.	39	40	1	0
Fill 5 pail from can A.	34	40	1	5
Fill 4 pail from 5 pail, leaving 2 quarts in 5 pail.	34	40	4	2
Empty 4 pail into can A.	38	40	0	2
Fill 4 pail from can B.	38	36	4	2
Pour from 4 pail into can A until A is filled, leaving 2 quarts in 4 pail.	40	36	2	2

Each pail now holds two quarts, can A is full, and can B is missing 4 quarts.