Question

A certain jewelry store sells customized rings in which three gemstones selected by the customer are set in a straight row along the band of the ring. if exactly 5 different types of gemstones are available, and if at least two of the gemstones in any given ring must be different, how many different rings are possible?

Answer 1

Let's assume the gemstones are A, B, C, D, E

1. A, B
2. A, C
3. A, D
4. A, E
5. B, C
6. B, D
7. B, E
8. C, D
9. C, E
10. D, E

A: 10 different rings are possible.

Hope this helps. - M