Formatting Time (MM:SS) without using hours and dates

I'm not looking for anything. The data in Column A is mm.ss (it's keyed in as a decimal, but A1 is supposed to represent 81 minutes, 20 seconds). This is easy for keying purposes, but obviously any summary total would be wrong as 0.20 is, mathematically, not 20 seconds).

Column D is three different versions of how the decimal data could be converted to time and totaled. Column A total is 222 minutes, 20 seconds, which can expressed as a decimal (222.33 minutes), or you could have it as 222.20 (mm.ss), or the traditional time format 222:20.

If I'm keying a lot of time data in the format mm:ss from hardcopy time logs, then I wouldn't want to key it in the traditional h:mm:ss format. I would enter it as a decimal as I'm faster at data input with a ten key using a decimal. But, 0.20 in decimal has to be converted if I intend it to represent 20 seconds when I total it.