Small Problem

Working a on project with units and time

1 unit = 5 minutes

I have a spread shee set up like this

Units Taken Standard Time Duration Time Converted

15 5 75 1:15


My problem is the Time Converted column

75 minutes = 1 and 15 minutes (1:15)

I want formula that converts the 75 into 1:15

Duration in Minutes Minutes Converted Into Hours
60 1:00
75 1:15
91 1:31
115 1:55



and so on


Please Help