would sound travel faster in a thick piece of metal (high density) or a large hallow piece of metal (low density) ? explain why.

Sound would travel in a thick piece of medal (high density) because sound travels best through solids. Therefore, the thicker, the easier sound can travel.

(I know for sure that sound travels best through solids but if the rest is wrong than I am sorry, though I don't think it is)

Sound would travel faster in a thick piece of metal since the molecules are closer together. However, since there are more molecules, it would be quieter on the other side than the hollow metal.