Let's see how many parts of recyclable aluminum there is in 1 pound.
16 / 5 = 3.2
There are 3.2 parts used per pound of recyclable aluminum. Now, let's multiply that by 2000 to see how many parts there are in a ton.
3.2 * 2000 = 6400
The factory must produce 6400 parts in order to gain 1 ton of recyclable aluminum.