Answer:
3.90 meters.
Explanation:
Since Amy needs ribbon for her art project, and she plans to buy 3.84 meters of that material, but the store only sells said product by the tenth of a meter, in order to get closer to the desired size she will have to buy 39 pieces of 10 cm (one tenth of a meter), that is, she must buy 3.90 meters, of which there will be 6 centimeters of the product left over.