A chain weighs 10 pounds per foot. How many ounces will 4 inches weigh?

If a chain weighs 10 pounds per foot, and a foot is 12 inches, and 16 ounces is a pound, then 4 inches is 10/3 pounds. 

Since 16 ounces are in a pound, there are 16 x 10/3 ounces in 4 inches of chain.

4 inches of chain weigh 160/3 ounces or 53.3333 ounces.

10 #/ft   *    1 ft / 12 inches    *    4 inches    *    16 oz / #    =    53.333 oz              (as proyaop found !)