what is the difference between a 5 decade rosary and a 7 decade rosary?

Answer 1

The Franciscan Crown, or "Rosary of the Seven Joys of the Blessed Virgin Mary" -- also known as the "Seraphic Rosary" -- is a 7-decade Rosary that focuses on the 7 Joys of Mary. It's an ancient Franciscan sacramental that has its origins in A.D. 1422. It originally consisted of one Our Father and 10 Hail Mary in honor of each of her Seven Joys -- the Annunciation; Visitation; Nativity; Adoration of the Magi; Finding Jesus in the Temple; Resurrection; and Assumption and Coronation of the Virgin.
Usual 5 decade Rosary
The purpose of the Rosary is to help keep in memory certain principal events or mysteries in the history of our salvation, and to thank and praise God for them. There are twenty mysteries reflected upon in the Rosary, and these are divided into the five JOYFUL MYSTERIES, the five LUMINOUS MYSTERIES, the five SORROWFUL MYSTERIES, and the five GLORIOUS MYSTERIES.
Seven Decade Rosary
Seven decades of 10 Hail Marys equal 70 Hail Marys, but two more were later added to make the total equal to seventy-two, the number of years that Our Lady is said to have lived on earth.

One may also add a Pater, Ave, and Gloria at the very end for the intentions of the Holy Fathe

Answer 2

A seven decade rosary is 20 years older than a five decade rosary.