IMC 2006 Q2
2. The diagram shows seven metal rings linked together. What is the smallest number of rings that need to be cut in order to separate all the rings?
- A 2
- B 3
- C 4
- D 5
- E 6
Intermediate Mathematical Challenge 2006, Question 2. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: B 3
The configuration includes three pairs of small rings. The rings in each pair are separate from the rings in the other two pairs so at least three rings will need to be cut. If the ring in each pair which is connected to the large ring is cut, then all of the rings can be separated. So the minimum number of rings which need to be cut is three.
Solution © UK Mathematics Trust, from the IMC 2006 solutions.