When the U. S. government needed 10,000 rifles for the army, Eli Whitney applied for the contract. He took several guns, dismantled them, put the pieces in a box, and shook it. He then randomly selected the pieces he needed, assembled on rifle, and fired it. What did he demonstrate

interchangeable parts.

Step-by-step explanation:

Eli Whitney here demonstrates interchangeable parts.He took several guns, dismantled them, put the pieces in a box, and shook it. He then randomly selected the pieces he needed, assembled on rifle, and fired it. popularized in America when Eli Whitney used them to assemble muskets in the first years of the 19th century, allowed comparatively unskilled workers to manufacture vast quantities of arms rapidly and at lower expense, and made repair and replacement of parts exponentially simpler.