5 . . . . . is multiplied by 5 to get . . . . . 25
25 . . . . . is multiplied by 5 to get . . . . . 125
so
125 . . . . . is multiplied by 5 to get . . . . . 625
625 . . . . . is multiplied by 5 to get . . . . . 3125
and
3125 . . . . . is multiplied by 5 to get . . . . . 15,625