Would not the Rosary be just as efficient if said with one Our Father, one Hail Mary, and one Gloria?

It would not be the Rosary then, but some other type of devotion. Nor would such a devotion be as efficient, for meditation whilst saying ten Hail Marys is better than meditation whilst saying one. But your trouble seems to be based on the mere question of number. That is quite immaterial.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty