There are 60 sec in every min 300  60 = 5

2) 180 min     = 3         hr
 

There are 60 min in every hour 180 60 = 3

3) 2 wk          = 14      day(s)
 

There are 7 days in every week 2 x 7 = 14

4) 1 decade    =  10     yrs
5) 1 Score      =  20     yrs
6) 1 Century   =  100   yrs
7) 1 Millenum =  1000 yrs