There are five chain links, each with 3 rings. What is the minimum number of rings that need to be unlinked and relinked to connect these links into one chain?

#
For connecting two links, one ring is required.

## Solution

Example: we unlock 3 rings from one link. The remaining 4 links are connected using the three unlocked rings.

Evaluation: if fewer than 3 rings are unlocked, at least 5 separate links will remain, which would require at least 4 unlocked rings to connect - a contradiction.

## Answer

3 rings.