Paper and barrel: what they have in common

1. Step 1. Paper — is material for — Loudspeaker. The cone is paper.
2. Step 2. Loudspeaker — is part of — Public address system. Loudspeakers.
3. Step 3. Public address system — is part of — Stadium. Sound.
4. Step 4. Stadium — works like — Amphitheatre. The Greek stadium is older than the Roman amphitheatre; modern stadiums combine both layouts.
5. Step 5. Amphitheatre — has part — Arch. Arcades.
6. Step 6. Arch — works like — Barrel. Staves squeezed by hoops hold their shape by the same compression as the stones of an arch.

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