Can the Chaplet Be Prayed on One Decade?

If you don’t have a full rosary, you can certainly pray a Chaplet of Divine Mercy on a single decade. You would simply progress through the single decade of beads five consecutive times, similar to how a person who has a rosary ring with ten nodules would pray the Chaplet or Rosary by turning their ring five times.

I also know a person with a chronic tennis-elbow problem for whom holding a rosary aggravates the condition. This person prays a Chaplet or rosary each day using ten fingers to keep track of the decades. One need not use an actual rosary to have one’s prayers count.